Separation Matrix

ABSTRACT

The invention relates to a separation matrix comprising at least 11 mg/ml Fc-binding ligands covalently coupled to a porous support, wherein:
         a) the ligands comprise multimers of alkali-stabilized Protein A domains, and   b) the porous support comprises cross-linked polymer particles having a volume-weighted median diameter (d50,v) of 56-70 micrometers and a dry solids weight of 55-80 mg/ml.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16,893,574, filed Jun. 5, 2020, which is a continuation of U.S.applciation Ser. No. 16/682,855, filed Nov. 13, 2019, now U.S. Pat. No.10,711,035, which is a continuation of U.S. application Ser. No.16/096,952, filed Oct. 26, 2018, now U.S. Pat. No. 10,513,537 issuedDec. 24, 2019, which claims the priority benefit of PCT/EP2017/061164filed on May 10, 2017 which claims priority benefit of U.S. applicationSer. No. 15/282,367, filed Sep. 30, 2016 and Great Britain ApplicationNos. 1608229.9 and 1608232.3, both of which were filed May 11, 2016. Theentire contents of which are hereby incorporated by reference herein.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted electronically in ASCII format and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Oct. 22, 2018, isnamed 313838A_ST25.txt and is 79,053 bytes in size.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of affinity chromatography,and more specifically to mutated immunoglobulin-binding domains ofProtein A, which are useful in affinity chromatography ofimmunoglobulins. The invention also relates to multimers of the mutateddomains and to separation matrices containing the mutated domains ormultimers.

BACKGROUND OF THE INVENTION

Immunoglobulins represent the most prevalent biopharmaceutical productsin either manufacture or development worldwide. The high commercialdemand for and hence value of this particular therapeutic market has ledto the emphasis being placed on pharmaceutical companies to maximize theproductivity of their respective mAb manufacturing processes whilstcontrolling the associated costs.

Affinity chromatography is used in most cases, as one of the key stepsin the purification of these immunoglobulin molecules, such asmonoclonal or polyclonal antibodies. A particularly interesting class ofaffinity reagents is proteins capable of specific binding to invariableparts of an immunoglobulin molecule, such interaction being independenton the antigen-binding specificity of the antibody. Such reagents can bewidely used for affinity chromatography recovery of immunoglobulins fromdifferent samples such as but not limited to serum or plasmapreparations or cell culture derived feed stocks. An example of such aprotein is staphylococcal protein A, containing domains capable ofbinding to the Fc and Fab portions of IgG immunoglobulins from differentspecies. These domains are commonly denoted as the E-, D-, A-, B- andC-domains.

Staphylococcal protein A (SpA) based reagents have due to their highaffinity and selectivity found a widespread use in the field ofbiotechnology, e.g. in affinity chromatography for capture andpurification of antibodies as well as for detection or quantification.At present, SpA-based affinity medium probably is the most widely usedaffinity medium for isolation of monoclonal antibodies and theirfragments from different samples including industrial cell culturesupernatants. Accordingly, various matrices comprising protein A-ligandsare commercially available, for example, in the form of native protein A(e.g. Protein A SEPHAROSE, GE Healthcare, Uppsala, Sweden) and alsocomprised of recombinant protein A (e.g. rProtein A-SEPHAROSE, GEHealthcare). More specifically, the genetic manipulation performed inthe commercial recombinant protein A product is aimed at facilitatingthe attachment thereof to a support and at increasing the productivityof the ligand.

These applications, like other affinity chromatography applications,require comprehensive attention to definite removal of contaminants.Such contaminants can for example be non-eluted molecules adsorbed tothe stationary phase or matrix in a chromatographic procedure, such asnon-desired biomolecules or microorganisms, including for exampleproteins, carbohydrates, lipids, bacteria and viruses. The removal ofsuch contaminants from the matrix is usually performed after a firstelution of the desired product, in order to regenerate the matrix beforesubsequent use. Such removal usually involves a procedure known ascleaning-in-place (CIP), wherein agents capable of eluting contaminantsfrom the stationary phase are used. One such class of agents often usedis alkaline solutions that are passed over said stationary phase. Atpresent the most extensively used cleaning and sanitizing agent is NaOH,and the concentration thereof can range from 0.1 up to e.g. 1 M,depending on the degree and nature of contamination. This strategy isassociated with exposing the matrix to solutions with pH-values above13. For many affinity chromatography matrices containing proteinaceousaffinity ligands such alkaline environment is a very harsh condition andconsequently results in decreased capacities owing to instability of theligand to the high pH involved.

An extensive research has therefore been focused on the development ofengineered protein ligands that exhibit an improved capacity towithstand alkaline pH-values. For example, Gülich et al. (SusanneGülich, Martin Linhult, Per-Åke Nygren, Mathias Uhlén, Sophia Hober,Journal of Biotechnology 80 (2000), 169-178) suggested proteinengineering to improve the stability properties of a Streptococcalalbumin-binding domain (ABD) in alkaline environments. Gülich et al.created a mutant of ABD, wherein all the four asparagine residues havebeen replaced by leucine (one residue), aspartate (two residues) andlysine (one residue). Further, Gülich et al. report that their mutantexhibits a target protein binding behavior similar to that of the nativeprotein, and that affinity columns containing the engineered ligand showhigher binding capacities after repeated exposure to alkaline conditionsthan columns prepared using the parental non-engineered ligand. Thus, itis concluded therein that all four asparagine residues can be replacedwithout any significant effect on structure and function.

Recent work shows that changes can also be made to protein A (SpA) toeffect similar properties. US patent application publication US2005/0143566, which is hereby incorporated by reference in its entirety,discloses that when at least one asparagine residue is mutated to anamino acid other than glutamine or aspartic acid, the mutation confersan increased chemical stability at pH-values of up to about 13-14compared to the parental SpA, such as the B-domain of SpA, or Protein Z,a synthetic construct derived from the B-domain of SpA (U.S. Pat. No.5,143,844, incorporated by reference in its entirety). The authors showthat when these mutated proteins are used as affinity ligands, theseparation media as expected can better withstand cleaning proceduresusing alkaline agents. Further mutations of protein A domains with thepurpose of increasing the alkali stability have also been published inU.S. Pat. No. 8,329,860, JP 2006304633A, U.S. Pat. No. 8,674,073, US2010/0221844, US 2012/0208234, U.S. Pat. No. 9,051,375, US 2014/0031522,US 2013/0274451 and WO 2014/146350, all of which are hereby incorporatedby reference in their entireties. However, the currently availablemutants are still sensitive to alkaline pH and the NaOH concentrationduring cleaning is usually limited to 0.1 M, which means that completecleaning is difficult to achieve. Higher NaOH concentrations, whichwould improve the cleaning, lead to unacceptable capacity losses.

There is thus still a need in this field to obtain a separation matrixcontaining protein ligands having a further improved stability towardsalkaline cleaning procedures. There is also a need for such separationmatrices with an improved binding capacity to allow for economicallyefficient purification of therapeutic antibodies.

SUMMARY OF THE INVENTION

One aspect of the invention is to provide a polypeptide with improvedalkaline stability. This is achieved with an Fc-binding polypeptidecomprising a mutant of a parental Fc-binding domain of StaphylococcusProtein A (SpA), as defined by, or having at least 80% such as at least90%, 95% or 98% identity to, SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO:3,SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:22, SEQID NO:51 or SEQ ID NO:52, wherein at least the asparagine or serineresidue at the position corresponding to position 11 in SEQ ID NO:4-7has been mutated to an amino acid selected from the group consisting ofglutamic acid, lysine, tyrosine, threonine, phenylalanine, leucine,isoleucine, tryptophan, methionine, valine, alanine, histidine andarginine. Alternatively, the polypeptide comprises a sequence as definedby, or having at least 80% or at least 90%, 95% or 98% identity to SEQID NO:53.

(SEQ ID NO: 53) X₁Q X₂AFYEILX₃LP NLTEEQRX₄X₅F IX₆X₇LKDX₈PSX₉SX₁₀X₁₁X₁₂LAEAKX₁₃ X₁₄NX₁₅AQwherein individually of each other:

-   X₁=A or Q or is deleted-   X₂=E,K,Y,T,F,L,W,I,M,V,A,H or R-   X₃=H or K-   X₄=A or N-   X₅=A, G, S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K-   X₆=Q or E-   X₇=S or K-   X₈=E or D-   X₉=Q or V or is deleted-   X₁₀=K,R or A or is deleted-   X₁₁=A,E or N or is deleted-   X₁₂=I or L-   X₁₃=K or R-   X₁₄=L or Y-   X₁₅=D, F,Y,W,K or R

One advantage is that the alkaline stability is improved over theparental polypeptides, with a maintained highly selective bindingtowards immunoglobulins and other Fc-containing proteins.

A second aspect of the invention is to provide a multimer with improvedalkaline stability, comprising a plurality of polypeptides. This isachieved with a multimer of the polypeptide disclosed above.

A third aspect of the invention is to provide a nucleic acid or a vectorencoding a polypeptide or multimer with improved alkaline stability.This is achieved with a nucleic acid or vector encoding a polypeptide ormultimer as disclosed above.

A fourth aspect of the invention is to provide an expression systemcapable of expressing a polypeptide or multimer with improved alkalinestability. This is achieved with an expression system comprising anucleic acid or vector as disclosed above.

A fifth aspect of the invention is to provide a separation matrixcapable of selectively binding immunoglobulins and other Fc-containingproteins and exhibiting an improved alkaline stability. This is achievedwith a separation matrix comprising at least 11 mg/ml Fc-binding ligandscovalently coupled to a porous support, wherein:

-   a) the ligands comprise multimers of alkali-stabilized Protein A    domains,-   b) the porous support comprises cross-linked polymer particles    having a volume-weighted median diameter (d50,v) of 56-70    micrometers and a dry solids weight of 55-80 mg/ml. Alternatively,    it is achieved with a separation matrix comprising at least 15 mg/ml    Fc-binding ligands covalently coupled to a porous support, wherein    said ligands comprise multimers of alkali-stabilized Protein A    domains.

One advantage is that a high dynamic binding capacity is provided. Afurther advantage is that a high degree of alkali stability is achieved.

A sixth aspect of the invention is to provide an efficient andeconomical method of isolating an immunoglobulin or other Fc-containingprotein. This is achieved with a method comprising the steps of:

-   a) contacting a liquid sample comprising an immunoglobulin with a    separation matrix as disclosed above,-   b) washing the separation matrix with a washing liquid,-   c) eluting the immunoglobulin from the separation matrix with an    elution liquid, and-   d) cleaning the separation matrix with a cleaning liquid.

Further suitable embodiments of the invention are described in thedependent claims. Co-pending applications PCT EP2015/076639, PCTEP2015/076642, GB 1608229.9 and GB 1608232.3 are hereby incorporated byreference in their entireties.

Definitions

The terms “antibody” and “immunoglobulin” are used interchangeablyherein, and are understood to include also fragments of antibodies,fusion proteins comprising antibodies or antibody fragments andconjugates comprising antibodies or antibody fragments.

The terms an “Fc-binding polypeptide” and “Fc-binding protein” mean apolypeptide or protein respectively, capable of binding to thecrystallisable part (Fc) of an antibody and includes e.g. Protein A andProtein G, or any fragment or fusion protein thereof that has maintainedsaid binding property.

The term “linker” herein means an element linking two polypeptide units,monomers or domains to each other in a multimer.

The term “spacer” herein means an element connecting a polypeptide or apolypeptide multimer to a support.

The term “% identity” with respect to comparisons of amino acidsequences is determined by standard alignment algorithms such as, forexample, Basic Local Alignment Tool (BLAST) described in Altshul et al.(1990) J. Mol. Biol., 215: 403-410. A web-based software for this isfreely available from the US National Library of Medicine atblast.ncbi.nlm.nih.gov/Blast.cgi?PROGRAM=blastp&PAGE_TYPE=BlastSearch&LINK_LOC=blasthome.Here, the algorithm “blastp (protein-protein BLAST)” is used foralignment of a query sequence with a subject sequence and determiningi.a. the % identity.

As used herein, the terms “comprises,” “comprising,” “containing,”“having” and the like can have the meaning ascribed to them in U.S.Patent law and can mean “includes,” “including,” and the like;“consisting essentially of” or “consists essentially” likewise has themeaning ascribed in U.S. Patent law and the term is open-ended, allowingfor the presence of more than that which is recited so long as basic ornovel characteristics of that which is recited is not changed by thepresence of more than that which is recited, but excludes prior artembodiments.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows an alignment of the Fc-binding domains as defined by SEQ IDNO:1-7 and 51-52.

FIG. 2 shows results from Example 2 for the alkali stability of parentaland mutated tetrameric Zvar (SEQ ID NO:7) polypeptide variants coupledto an SPR biosensor chip.

FIG. 3 shows results from Example 4 for the alkali stability (0.5 MNaOH) of parental and mutated tetrameric Zvar (SEQ ID NO:7) polypeptidevariants coupled to agarose beads.

FIG. 4 shows results from Example 4 for the alkali stability (1.0 MNaOH) of parental and mutated tetrameric Zvar (SEQ ID NO:7) polypeptidevariants coupled to agarose beads.

FIG. 5 shows results from Example 7 for the alkali stability (1.0 MNaOH) of agarose beads with different amounts of mutated multimervariants (SEQ ID NO:20) coupled. The results are plotted as the relativeremaining dynamic capacity (Qb10%, 6 min residence time) vs. incubationtime in 1 M NaOH.

FIG. 6 shows results from Example 7 for the alkali stability (1.0 MNaOH) of agarose beads with different amounts of mutated multimervariants (SEQ ID NO:20) coupled. The results are plotted as the relativeremaining dynamic capacity (Qb10%, 6 min residence time) after 31 hincubation in 1 M NaOH vs. the ligand content of the prototypes.

DETAILED DESCRIPTION OF EMBODIMENTS

In one aspect the present invention discloses an Fc-binding polypeptide,which comprises, or consists essentially of, a mutant of an Fc-bindingdomain of Staphylococcus Protein A (SpA), as defined by, or having atleast 90%, at least 95% or at least 98% identity to, SEQ ID NO:1(E-domain), SEQ ID NO:2 (D-domain), SEQ ID NO:3 (A-domain), SEQ ID NO:22(variant A-domain), SEQ ID NO:4 (B-domain), SEQ ID NO:5 (C-domain), SEQID NO:6 (Protein Z), SEQ ID NO:7 (Zvar), SEQ ID NO:51 (Zvar without thelinker region amino acids 1-8 and 56-58) or SEQ ID NO:52 (C-domainwithout the linker region amino acids 1-8 and 56-58) as illustrated inFIG. 1, wherein at least the asparagine (or serine, in the case of SEQID NO:2) residue at the position* corresponding to position 11 in SEQ IDNO:4-7 has been mutated to an amino acid selected from the groupconsisting of glutamic acid, lysine, tyrosine, threonine, phenylalanine,leucine, isoleucine, tryptophan, methionine, valine, alanine, histidineand arginine. Protein Z (SEQ ID NO:6) is a mutated B-domain as disclosedin U.S. Pat. No 5,143,844, hereby incorporated by reference in itsentirety, while SEQ ID NO:7 denotes a further mutated variant of ProteinZ, here called Zvar, with the mutations N3A,N6D,N23T. SEQ ID NO:22 is anatural variant of the A-domain in Protein A from Staphylococcus aureusstrain N315, having an A46S mutation, using the position terminology ofFIG. 1. The mutation of N11 in these domains confers an improved alkalistability in comparison with the parental domain/polypeptide, withoutimpairing the immunoglobulin-binding properties. Hence, the polypeptidecan also be described as an Fc- or immunoglobulin-binding polypeptide,or alternatively as an Fc- or immunoglobulin-binding polypeptide unit.

Throughout this description, the amino acid residue position numberingconvention of FIG. 1 is used, and the position numbers are designated ascorresponding to those in SEQ ID NO:4-7. This applies also to multimers,where the position numbers designate the positions in the polypeptideunits or monomers according to the convention of FIG. 1.

(truncated Zvar) SEQ ID NO: 51QQ NAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQ(truncated C domain) SEQ ID NO: 52QQ NAFYEILHLP NLTEEQRNGF IQSLKDDPSV SKEILAEAKK LNDAQ

In alternative language, the invention discloses an Fc-bindingpolypeptide which comprises a sequence as defined by, or having at least90%, at least 95% or at least 98% identity to SEQ ID NO:53.

SEQ ID NO: 53 X₁Q X₂AFYEILX₃LP NLTEEQRX₄X₅F IX₆X₇LKDX₈PSX₉SX₁₀X₁₁X₁₂LAEAKX₁₃ X₁₄NX₁₅AQwherein individually of each other:

-   X₁=A, Q or is deleted-   X₂=E,K,Y,T,F,L,W,I,M,V,A,H or R-   X₃=H or K-   X₄=A or N-   X₅=A, G, S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K, such as    S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K-   X₆=Q or E-   X₇=S or K-   X₈=E or D-   X₉=Q, V or is deleted-   X₁₀=K, R, A or is deleted-   X₁₁=A, E, N or is deleted-   X₁₂=I or L-   X₁₃=K or R-   X₁₄=L or Y-   X₁₅=D, F,Y,W,K or R

Specifically, the amino acid residues in SEQ ID NO:53 may individuallyof each other be:

-   X₁=A or is deleted-   X₂=E-   X₃=H-   X₄=N-   X₆=Q-   X₇=S-   X₈=D-   X₉=V or is deleted-   X₁₀=K or is deleted-   X₁₁=A or is deleted-   X₁₂=I-   X₁₃=K-   X₁₄=L.

In certain embodiments, the amino acid residues in SEQ ID NO:53 may be:X₁=A, X₂=E, X₃=H, X₄=N, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁=A, X₁₂=I,X₁₃=K, X₁₄=L. In some embodiments X₂=E, X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S,X₈=D, X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D and one or more of X₁, X₉, X₁₀ andX₁₁ is deleted. In further embodiments, X₁=A, X₂=E, X₃=H, X₄=N,X₅=S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K , X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K,X₁₁=A, X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D, or alternatively X₁=A, X₂=E, X₃=H,X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁=A, X₁₂=I, X₁₃=K, X₁₄=Land X₁₅=F,Y,W,K or R.

The N11 (X₂) mutation (e.g. a N11E or N11K mutation) may be the onlymutation or the polypeptide may also comprise further mutations, such assubstitutions in at least one of the positions corresponding topositions 3, 6, 9, 10, 15, 18, 23, 28, 29, 32, 33, 36, 37, 40, 42, 43,44, 47, 50, 51, 55 and 57 in SEQ ID NO:4-7. In one or more of thesepositions, the original amino acid residue may e.g. be substituted withan amino acid which is not asparagine, proline or cysteine. The originalamino acid residue may e.g. be substituted with an alanine, a valine, athreonine, a serine, a lysine, a glutamic acid or an aspartic acid.Further, one or more amino acid residues may be deleted, e.g. frompositions 1-6 and/or from positions 56-58.

In some embodiments, the amino acid residue at the positioncorresponding to position 9 in SEQ ID NO:4-7 (X₁) is an amino acid otherthan glutamine, asparagine, proline or cysteine, such as an alanine orit can be deleted. The combination of the mutations at positions 9 and11 provides particularly good alkali stability, as shown by theexamples. In specific embodiments, in SEQ ID NO: 7 the amino acidresidue at position 9 is an alanine and the amino acid residue atposition 11 is a lysine or glutamic acid, such as a lysine. Mutations atposition 9 are also discussed in copending applicationPCT/SE2014/050872, which is hereby incorporated by reference in itsentirety.

In some embodiments, the amino acid residue at the positioncorresponding to position 50 in SEQ ID NO:4-7 (X₁₃) is an arginine or aglutamic acid.

In certain embodiments, the amino acid residue at the positioncorresponding to position 3 in SEQ ID NO:4-7 is an alanine and/or theamino acid residue at the position corresponding to position 6 in SEQ IDNO:4-7 is an aspartic acid. One of the amino acid residues at positions3 and 6 may be an asparagine and in an alternative embodiment both aminoacid residues at positions 3 and 6 may be asparagines.

In some embodiments the amino acid residue at the position correspondingto position 43 in SEQ ID NO:4-7 (X₁₁) is an alanine or a glutamic acid,such as an alanine or it can be deleted. In specific embodiments, theamino acid residues at positions 9 and 11 in SEQ ID NO: 7 are alanineand lysine/glutamic acid respectively, while the amino acid residue atposition 43 is alanine or glutamic acid.

In certain embodiments the amino acid residue at the positioncorresponding to position 28 in SEQ ID NO:4-7 (X₅) is an alanine or anasparagine, such as an alanine.

In some embodiments the amino acid residue at the position correspondingto position 40 in SEQ ID NO:4-7 (X₉) is selected from the groupconsisting of asparagine, alanine, glutamic acid and valine, or from thegroup consisting of glutamic acid and valine or it can be deleted. Inspecific embodiments, the amino acid residues at positions 9 and 11 inSEQ ID NO: 7 are alanine and glutamic acid respectively, while the aminoacid residue at position 40 is valine. Optionally, the amino acidresidue at position 43 may then be alanine or glutamic acid.

In certain embodiments, the amino acid residue at the positioncorresponding to position 42 in SEQ ID NO:4-7 (X₁₀) is an alanine,lysine or arginine or it can be deleted.

In some embodiments the amino acid residue at the position correspondingto position 18 in SEQ ID NO:4-7 (X₃) is a lysine or a histidine, such asa lysine.

In certain embodiments the amino acid residue at the positioncorresponding to position 33 in SEQ ID NO:4-7 (X₇) is a lysine or aserine, such as a lysine.

In some embodiments the amino acid residue at the position correspondingto position 37 in SEQ ID NO:4-7 (X₈) is a glutamic acid or an asparticacid, such as a glutamic acid.

In certain embodiments the amino acid residue at the positioncorresponding to position 51 in SEQ ID NO:4-7 (X₁₄) is a tyrosine or aleucine, such as a tyrosine.

In some embodiments, the amino acid residue at the positioncorresponding to position 44 in SEQ ID NO:4-7 (X₁₂) is a leucine or anisoleucine. In specific embodiments, the amino acid residues atpositions 9 and 11 in SEQ ID NO: 7 are alanine and lysine/glutamic acidrespectively, while the amino acid residue at position 44 is isoleucine.Optionally, the amino acid residue at position 43 may then be alanine orglutamic acid.

In some embodiments, the amino acid residues at the positionscorresponding to positions 1, 2, 3 and 4 or to positions 3, 4, 5 and 6in SEQ ID NO: 4-7 have been deleted. In specific variants of theseembodiments, the parental polypeptide is the C domain of Protein A

(SEQ ID NO: 5). The effects of these deletions on the native C domainare described in U.S. Pat. No. 9,018,305 and U.S. Pat. No. 8,329,860,which are hereby incorporated by reference in their entireties.

In certain embodiments, the mutation in SEQ ID NO:4-7, such as in SEQ IDNO:7, is selected from the group consisting of:N11K; N11E; N11Y; N11T;N11F; N11L; N11W; N11I; N11M; N11V; N11A; N11H; N11R; N11E,Q32A;N11E,Q32E,Q40E; N11E,Q32E,K5OR; Q9A,N11E,N43A; Q9A,N11E,N28A,N43A;Q9A,N11E,Q40V,A42K,N43E,L44I; Q9A,N11E,Q40V,A42K,N43A,L44I;N11K,H18K,S33K,D37E,A42R,N43A,L44I,K5OR,L51Y;Q9A,N11E,N28A,Q40V,A42K,N43A,L44I;Q9A,N11K,H18K,S33K,D37E,A42R,N43A,L44I,K5OR,L51Y; N11K, H18K, D37E,A42R, N43A, L44I; Q9A, N11K, H18K, D37E, A42R, N43A, L44I; Q9A, N11K,H18K, D37E, A42R, N43A, L44I, K5OR; Q9A,N11K,H18K,D37E,A42R;Q9A,N11E,D37E,Q40V,A42K,N43A,L44I and Q9A,N11E,D37E,Q40V,A42R,N43A,L44I.These mutations provide particularly high alkaline stabilities. Themutation in SEQ ID NO:4-7, such as in SEQ ID NO:7, can also be selectedfrom the group consisting of N11K; N11Y; N11F; N11L; N11W; N11I; N11M;N11V; N11A; N11H; N11R; Q9A,N11E,N43A; Q9A,N11E,N28A,N43A;Q9A,N11E,Q40V,A42K,N43E,L44I; Q9A,N11E,Q40V,A42K,N43A,L44I;Q9A,N11E,N28A,Q40V,A42K,N43A,L44I;N11K,H18K,S33K,D37E,A42R,N43A,L44I,K5OR,L51Y;Q9A,N11K,H18K,S33K,D37E,A42R,N43A,L44I,K5OR,L51Y; N11K, H18K, D37E,A42R, N43A, L44I; Q9A, N11K, H18K, D37E, A42R, N43A, L44I and Q9A, N11K,H18K, D37E, A42R, N43A, L44I, K5OR.

In some embodiments, the polypeptide comprises or consists essentiallyof a sequence defined by or having at least 90%, 95% or 98% identity toan amino acid sequence selected from the group consisting of: SEQ IDNO:8, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:12, SEQ IDNO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:23, SEQ IDNO:24, SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ IDNO:29, SEQ ID NO:36, SEQ ID NO:37, SEQ ID NO:38, SEQ ID NO:39, SEQ IDNO:40, SEQ ID NO:41, SEQ ID NO:42, SEQ ID NO:43, SEQ ID NO:44, SEQ IDNO:45, SEQ ID NO:46, SEQ ID NO:47, SEQ ID NO:48, SEQ ID NO:49 and SEQ IDNO:50. It may e.g. comprise or consist essentially of a sequence definedby or having at least 90%, 95% or 98% identity to an amino acid sequenceselected from the group consisting of: SEQ ID NO:8, SEQ ID NO:9, SEQ IDNO:10, SEQ ID NO:11, SEQ ID NO:16, SEQ ID NO:23, SEQ ID NO:24, SEQ IDNO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28 and SEQ ID NO:29. It canalso comprise or consist essentially of a sequence defined by or havingat least 90%, 95% or 98% identity to an amino acid sequence selectedfrom the group consisting of: SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO:10,SEQ ID NO:11, SEQ ID NO:16, SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25,SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:38, SEQ ID NO:40; SEQ ID NO:41;SEQ ID NO:42; SEQ NO:43, SEQ ID NO:44, SEQ ID NO:45, SEQ ID NO:46, SEQID NO:47 and SEQ ID NO:48.

In certain embodiments, the polypeptide comprises or consistsessentially of a sequence defined by or having at least 90%, 95% or 98%identity to an amino acid sequence selected from the group consisting ofSEQ ID NO:54-70. comprises or consists essentially of a sequence definedby or having at least 90%, 95% or 98% identity to an amino acid sequenceselected from the group consisting of SEQ ID NO:71-75, or it maycomprise or consist essentially of a sequence defined by or having atleast 90%, 95% or 98% identity to an amino acid sequence selected fromthe group consisting of SEQ ID NO:76-79. It may further comprise orconsist essentially of a sequence defined by or having at least 90%, 95%or 98% identity to an amino acid sequence selected from the groupconsisting of SEQ ID NO:89-95.

The polypeptide may e.g. be defined by a sequence selected from thegroups above or from subsets of these groups, but it may also compriseadditional amino acid residues at the N- and/or C-terminal end, e.g. aleader sequence at the N-terminal end and/or a tail sequence at theC-terminal end.

Zvar(Q9A, N11E, N43A) SEQ ID NO: 8VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SAALLAEAKK LNDAQAPKZvar(Q9A, N11E, N28A, N43A) SEQ ID NO: 9VDAKFDKEAQ EAFYEILHLP NLTEEQRAAF IQSLKDDPSQ SAALLAEAKK LNDAQAPKZvar(Q9A, N11E, Q40V, A42K, N43E, L44I) SEQ ID NO: 10VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKEILAEAKK LNDAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I) SEQ ID NO: 11VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(N11E, Q32A) SEQ ID NO: 12VDAKFDKEQQ EAFYEILHLP NLTEEQRNAF IASLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11E) SEQ ID NO: 13VDAKFDKEQQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11E, Q32E, Q40E) SEQ ID NO: 14VDAKFDKEQQ EAFYEILHLP NLTEEQRNAF IESLKDDPSE SANLLAEAKK LNDAQAPKZvar(N11E, Q32E, K50R) SEQ ID NO: 15VDAKFDKEQQ EAFYEILHLP NLTEEQRNAF IESLKDDPSQ SANLLAEAKR LNDAQAPKZvar(N11K) SEQ ID NO: 16VDAKFDKEQQ KAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11K, H18K, S33K, D37E, A42R, N43A, L44I, K50R, L51Y) SEQ ID NO: 23VDAKFDKEQQ KAFYEILKLP NLTEEQRNAF IQKLKDEPSQ SRAILAEAKR YNDAQAPKZvar(Q9A, N11E, N28A, Q40V, A42K, N43A, L44I) SEQ ID NO: 24VDAKFDKEAQ EAFYEILHLP NLTEEQRAAF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11K, H18K,S33K, D37E, A42R, N43A, L44I, K50R, L51Y)SEQ ID NO: 25 VDAKFDKEAQ KAFYEILKLP NLTEEQRAAF IQKLKDEPSQ SRAILAEAKRYNDAQAPK Zvar(N11K, H18K, D37E, A42R, N43A, L44I) SEQ ID NO: 26VDAKFDKEQQ KAFYEILKLP NLTEEQRNAF IQSLKDEPSQ SRAILAEAKK LNDAQAPKZvar(Q9A, N11K, H18K, D37E, A42R, N43A, L44I) SEQ ID NO: 27VDAKFDKEAQ KAFYEILKLP NLTEEQRNAF IQSLKDEPSQ SRAILAEAKK LNDAQAPKZvar(Q9A, N11K, H18K, D37E, A42R, N43A, L44I, K50R) SEQ ID NO: 28VDAKFDKEAQ KAFYEILKLP NLTEEQRNAF IQSLKDEPSQ SRAILAEAKR LNDAQAPKZvar(Q9A, N11K, H18K, D37E, A42R) SEQ ID NO: 29VDAKFDKEAQ KAFYEILKLP NLTEEQRNAF IQSLKDEPSQ SRNLLAEAKK LNDAQAPKB(Q9A, N11E, Q40V, A42K, N43A, L44I) SEQ ID NO: 36ADNKFNKEAQ EAFYEILHLP NLNEEQRNGF IQSLKDDPSV SKAILAEAKK LNDAQAPKC(Q9A, N11E, E43A) SEQ ID NO: 37ADNKFNKEAQ EAFYEILHLP NLTEEQRNGF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(N11Y) SEQ ID NO: 38VDAKFDKEQQ YAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11T) SEQ ID NO: 39VDAKFDKEQQ TAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11F) SEQ ID NO: 40VDAKFDKEQQ FAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11L) SEQ ID NO: 41VDAKFDKEQQ LAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11W) SEQ ID NO: 42VDAKFDKEQQ WAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11I) SEQ ID NO: 43VDAKFDKEQQ IAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11M) SEQ ID NO: 44VDAKFDKEQQ MAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11V) SEQ ID NO: 45VDAKFDKEQQ VAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11A) SEQ ID NO: 46VDAKFDKEQQ AAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11H) SEQ ID NO: 47VDAKFDKEQQ HAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(N11R) SEQ ID NO: 48VDAKFDKEQQ RAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SANLLAEAKK LNDAQAPKZvar(Q9A, N11E, D37E, Q40V, A42K, N43A, L44I) SEQ ID NO: 49VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDEPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, D37E, Q40V, A42R, N43A, L44I) SEQ ID NO: 50VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDEPSV SRAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29G, Q40V, A42K, N43A, L44I) SEQ ID NO: 54VDAKFDKEAQ EAFYEILHLP NLTEEQRNGF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29S, Q40V, A42K, N43A, L44I) SEQ ID NO: 55VDAKFDKEAQ EAFYEILHLP NLTEEQRNSF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29Y, Q40V, A42K, N43A, L44I) SEQ ID NO: 56VDAKFDKEAQ EAFYEILHLP NLTEEQRNYF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29Q, Q40V, A42K, N43A, L44I) SEQ ID NO: 57VDAKFDKEAQ EAFYEILHLP NLTEEQRNQF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29T, Q40V, A42K, N43A, L44I) SEQ ID NO: 58VDAKFDKEAQ EAFYEILHLP NLTEEQRNTF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29N, Q40V, A42K, N43A, L44I) SEQ ID NO: 59VDAKFDKEAQ EAFYEILHLP NLTEEQRNNF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29F, Q40V, A42K, N43A, L44I) SEQ ID NO: 60VDAKFDKEAQ EAFYEILHLP NLTEEQRNFF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29L, Q40V, A42K, N43A, L44I) SEQ ID NO: 61VDAKFDKEAQ EAFYEILHLP NLTEEQRNLF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29W, Q40V, A42K, N43A, L44I) SEQ ID NO: 62VDAKFDKEAQ EAFYEILHLP NLTEEQRNWF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29I, Q40V, A42K, N43A, L44I) SEQ ID NO: 63VDAKFDKEAQ EAFYEILHLP NLTEEQRNIF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29M, Q40V, A42K, N43A, L44I) SEQ ID NO: 64VDAKFDKEAQ EAFYEILHLP NLTEEQRNMF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29V, Q40V, A42K ,N43A, L44I) SEQ ID NO: 65VDAKFDKEAQ EAFYEILHLP NLTEEQRNVF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29D, Q40V, A42K, N43A, L44I) SEQ ID NO: 66VDAKFDKEAQ EAFYEILHLP NLTEEQRNDF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29E, Q40V, A42K, N43A, L44I) SEQ ID NO: 67VDAKFDKEAQ EAFYEILHLP NLTEEQRNEF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29H, Q40V, A42K, N43A, L44I) SEQ ID NO: 68VDAKFDKEAQ EAFYEILHLP NLTEEQRNHF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29R, Q40V, A42K, N43A, L44I) SEQ ID NO: 69VDAKFDKEAQ EAFYEILHLP NLTEEQRNRF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, A29K, Q40V, A42K, N43A, L44I) SEQ ID NO: 70VDAKFDKEAQ EAFYEILHLP NLTEEQRNKF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I, D53F) SEQ ID NO: 71VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNFAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I, D53Y) SEQ ID NO: 72VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNYAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I, D53W) SEQ ID NO: 73VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNWAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I, D53K) SEQ ID NO: 74VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNKAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I, D53R) SEQ ID NO: 75VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNRAQAPKZvar(Q9del, N11E, Q40V, A42K, N43A, L44I) SEQ ID NO: 76VDAKFDKE_Q EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, Q40del, A42K, N43A, L44I) SEQ ID NO: 77VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPS_ SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, Q40V, A42del, N43A, L44I) SEQ ID NO: 78VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV S_AILAEAKK LNDAQAPKZvar(Q9A, N11E, Q40V, A42K, N43del, L44I) SEQ ID NO: 79VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SK_ILAEAKK LNDAQAPKZvar(D2del, A3del, K4del, Q9A, N11E, Q40V, A42K, N43A, L44I)SEQ ID NO: 89 V___FDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK Zvar(V1del, D2del, Q9A, N11E, Q40V, A42K, N43A, L44I, K58del)SEQ ID NO: 90 __AKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAP_ Zvar(K4del, F5del, D6del, K7del, E8del, Q9A, N11E, Q40V, A42K,N43A, L44I) SEQ ID NO: 91VDA_____AQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I, A56del, P57del, K58del)SEQ ID NO: 92 VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQ___ Zvar(V1del,, D2del, A3del, Q9A, N11E, Q40V, A42K, N43A, L44I)SEQ ID NO: 93 ___KFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK Zvar(V1del, D2del, A3del, K4del, F5del, D6del, K7del, E8del,Q9A, N11E, Q40V, A42K, N43A, L44I) SEQ ID NO: 94________AQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKZvar(Q9A, N11E, Q40V, A42K, N43A, L44I, K58_insYEDG) SEQ ID NO: 95VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKYE DG

In a second aspect the present invention discloses a multimercomprising, or consisting essentially of, a plurality of polypeptideunits as defined by any embodiment disclosed above. The use of multimersmay increase the immunoglobulin binding capacity and multimers may alsohave a higher alkali stability than monomers. The multimer can e.g. be adimer, a trimer, a tetramer, a pentamer, a hexamer, a heptamer, anoctamer or a nonamer. It can be a homomultimer, where all the units inthe multimer are identical or it can be a heteromultimer, where at leastone unit differs from the others. Advantageously, all the units in themultimer are alkali stable, such as by comprising the mutationsdisclosed above. The polypeptides can be linked to each other directlyby peptide bonds between the C-terminal and N-terminal ends of thepolypeptides. Alternatively, two or more units in the multimer can belinked by linkers comprising oligomeric or polymeric species, such aslinkers comprising peptides with up to 25 or 30 amino acids, such as3-25 or 3-20 amino acids. The linkers_may e.g. comprise or consistessentially of a peptide sequence defined by, or having at least 90%identity or at least 95% identity, with an amino acid sequence selectedfrom the group consisting of APKVDAKFDKE (SEQ ID NO:96), APKVDNKFNKE(SEQ ID NO:97), APKADNKFNKE (SEQ ID NO:98), APKVFDKE (SEQ ID NO:99),APAKFDKE (SEQ ID NO:100), AKFDKE (SEQ ID NO:101), APKVDA (SEQ IDNO:102), VDAKFDKE (SEQ ID NO:103), APKKFDKE (SEQ ID NO:104), APK,APKYEDGVDAKFDKE (SEQ ID NO:105) and YEDG (SEQ ID NO:106) oralternatively selected from the group consisting of APKADNKFNKE (SEQ IDNO:98), APKVFDKE (SEQ ID NO:99), APAKFDKE (SEQ ID NO:100), AKFDKE (SEQID NO:101), APKVDA (SEQ ID NO:102), VDAKFDKE (SEQ ID NO:103), APKKFDKE(SEQ ID NO:104), APKYEDGVDAKFDKE (SEQ ID NO:105) and YEDG (SEQ IDNO:106). They can also consist essentially of a peptide sequence definedby or having at least 90% identity or at least 95% identity with anamino acid sequence selected from the group consisting of APKADNKFNKE(SEQ ID NO:98), APKVFDKE (SEQ ID NO:99), APAKFDKE (SEQ ID NO:100),AKFDKE (SEQ ID NO:101), APKVDA (SEQ ID NO:102), VDAKFDKE (SEQ IDNO:103), APKKFDKE (SEQ ID NO:104), APK and APKYEDGVDAKFDKE (SEQ IDNO:105). In some embodiments the linkers do not consist of the peptidesAPKVDAKFDKE (SEQ ID NO:96) or APKVDNKFNKE (SEQ ID NO:97), oralternatively do not consist of the peptides APKVDAKFDKE (SEQ ID NO:96),APKVDNKFNKE (SEQ ID NO:97).

The nature of such a linker should preferably not destabilize thespatial conformation of the protein units. This can e.g. be achieved byavoiding the presence of proline in the linkers. Furthermore, saidlinker should preferably also be sufficiently stable in alkalineenvironments not to impair the properties of the mutated protein units.For this purpose, it is advantageous if the linkers do not containasparagine. It can additionally be advantageous if the linkers do notcontain glutamine. The multimer may further at the N-terminal endcomprise a plurality of amino acid residues e.g. originating from thecloning process or constituting a residue from a cleaved off signalingsequence. The number of additional amino acid residues may e.g. be 20 orless, such as 15 or less, such as 10 or less or 5 or less. As a specificexample, the multimer may comprise an AQ, AQGT (SEQ ID NO:107), VDAKFDKE(SEQ ID NO:103), AQVDAKFDKE (SEQ ID NO:108) or AQGTVDAKFDKE (SEQ IDNO:109) sequence at the N-terminal end.

In certain embodiments, the multimer may comprise, or consistessentially, of a sequence selected from the group consisting of: SEQ IDNO:80-87. These and additional sequences are listed below and named asParent(Mutations)n, where n is the number of monomer units in amultimer.

Zvar(Q9A, N11E, N43A)4 SEQ ID NO: 17AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSQ SAALLAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSQSAALLAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAFIQSLKDDPSQ SAALLAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLPNLTEEQRNAF IQSLKDDPSQ SAALLAEAKK LNDAQAPKC Zvar(Q9A, N11E, N28A, N43A)4SEQ ID NO: 18AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRAAF IQSLKDDPSQ SAALLAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRAAF IQSLKDDPSQSAALLAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRAAFIQSLKDDPSQ SAALLAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLPNLTEEQRAAF IQSLKDDPSQ SAALLAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43E, L44I)4 SEQ ID NO: 19AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKEILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKEILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKEILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKEILAEAKKLNDAQAPKC Zvar(Q9A, N11E, Q40V, A42K, N43A, L44I)4 SEQ ID NO: 20AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPKC Zvar(N11K, H18K, S33K, D37E, A42R, N43A, L44I, K50R, L51Y)4SEQ ID NO: 30AQGT VDAKFDKEQQ KAFYEILKLP NLTEEQRNAF IQKLKDEPSQ SRAILAEAKRYNDAQAPK VDAKFDKEQQ KAFYEILKLP NLTEEQRNAF IQKLKDEPSQSRAILAEAKR YNDAQAPK VDAKFDKEQQ KAFYEILKLP NLTEEQRNAFIQKLKDEPSQ SRAILAEAKR YNDAQAPK VDAKFDKEQQ KAFYEILKLPNLTEEQRNAF IQKLKDEPSQ SRAILAEAKR YNDAQAPKCZvar(Q9A, N11K, H18K, D37E, A42R)4 SEQ ID NO: 31AQGT VDAKFDKEAQ KAFYEILKLP NLTEEQRNAF IQSLKDEPSQ SRNLLAEAKKLNDAQAPK VDAKFDKEAQ KAFYEILKLP NLTEEQRNAF IQSLKDEPSQSRNLLAEAKK LNDAQAPK VDAKFDKEAQ KAFYEILKLP NLTEEQRNAFIQSLKDEPSQ SRNLLAEAKK LNDAQAPK VDAKFDKEAQ KAFYEILKLPNLTEEQRNAF IQSLKDEPSQ SRNLLAEAKK LNDAQAPKCZvar(Q9A, N11E, N28A, Q40V, A42K, N43A, L44I)4 SEQ ID NO: 32AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRAAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRAAF IQSLKDDPSVSKAILAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRAAFIQSLKDDPSV SKAILAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLPNLTEEQRAAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)6 SEQ ID NO: 33AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPKC Zvar(Q9A, N11E, D37E, Q40V, A42K, N43A, L44I)4 SEQ ID NO: 34AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDEPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDEPSVSKAILAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAFIQSLKDEPSV SKAILAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLPNLTEEQRNAF IQSLKDEPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, D37E, Q40V, A42R, N43A, L44I)4 SEQ ID NO: 35AQGT VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDEPSV SRAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDEPSVSRAILAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAFIQSLKDEPSV SRAILAEAKK LNDAQAPK VDAKFDKEAQ EAFYEILHLPNLTEEQRNAF IQSLKDEPSV SRAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)2 with D2, A3 andK4 in linker deleted SEQ ID NO: 80VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)2 with K58, V1 andD2 in linker deleted SEQ ID NO: 81VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAP AKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)2 with P57, K58, V1,D2 and A3 in linker deleted SEQ ID NO: 82VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAP AKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)2 with K4, F5, D6,K7 and E8 in linker deleted SEQ ID NO: 83VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)2 with A56, P57 andK58 in linker deleted SEQ ID NO: 84VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQVDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)2 with V1, D2 and A3in linker deleted SEQ ID NO: 85VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK KFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A,L44I)2 with V1, D2, A3, K4,F5, D6, K7 and E8 in linker deleted SEQ ID NO: 86VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK AQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKK LNDAQAPKCZvar(Q9A, N11E, Q40V, A42K, N43A, L44I)2 with YEDG insertedin linker between K58 and V1 SEQ ID NO: 87VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK YEDG VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSVSKAILAEAKK LNDAQAPKC Zvar2 SEQ ID NO: 88VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSV SKAILAEAKKLNDAQAPK VDAKFDKEAQ EAFYEILHLP NLTEEQRNAF IQSLKDDPSVSKAILAEAKK LNDAQAPKC

In some embodiments, the polypeptide and/or multimer, as disclosedabove, further comprises at the C-terminal or N-terminal end one or morecoupling elements, selected from the group consisting of one or morecysteine residues, a plurality of lysine residues and a plurality ofhistidine residues. The coupling element(s) may also be located within1-5 amino acid residues, such as within 1-3 or 1-2 amino acid residuesfrom the C-terminal or N-terminal end. The coupling element may e.g. bea single cysteine at the C-terminal end. The coupling element(s) may bedirectly linked to the C- or N-terminal end, or it/they may be linkedvia a stretch comprising up to 15 amino acids, such as 1-5, 1-10 or 5-10amino acids. This stretch should preferably also be sufficiently stablein alkaline environments not to impair the properties of the mutatedprotein. For this purpose, it is advantageous if the stretch does notcontain asparagine. It can additionally be advantageous if the stretchdoes not contain glutamine. An advantage of having a C-terminal cysteineis that endpoint coupling of the protein can be achieved throughreaction of the cysteine thiol with an electrophilic group on a support.This provides excellent mobility of the coupled protein which isimportant for the binding capacity.

The alkali stability of the polypeptide or multimer can be assessed bycoupling it to an SPR chip, e.g. to Biacore CM5 sensor chips asdescribed in the examples, using e.g. NHS- or maleimide couplingchemistries, and measuring the immunoglobulin-binding capacity of thechip, typically using polyclonal human IgG, before and after incubationin alkaline solutions at a specified temperature, e.g. 22 +/−2° C. Theincubation can e.g. be performed in 0.5 M NaOH for a number of 10 mincycles, such as 100, 200 or 300 cycles. The IgG capacity of the matrixafter 100 10 min incubation cycles in 0.5 M NaOH at 22 +/−2° C. can beat least 55, such as at least 60, at least 80 or at least 90% of the IgGcapacity before the incubation. Alternatively, the remaining IgGcapacity after 100 cycles for a particular mutant measured as above canbe compared with the remaining IgG capacity for the parentalpolypeptide/multimer. In this case, the remaining IgG capacity for themutant may be at least 105%, such as at least 110%, at least 125%, atleast 150% or at least 200% of the parental polypeptide/multimer.

In a third aspect the present invention discloses a nucleic acidencoding a polypeptide or multimer according to any embodiment disclosedabove. Thus, the invention encompasses all forms of the present nucleicacid sequence such as the RNA and the DNA encoding the polypeptide ormultimer. The invention embraces a vector, such as a plasmid, which inaddition to the coding sequence comprises the required signal sequencesfor expression of the polypeptide or multimer according the invention.In one embodiment, the vector comprises nucleic acid encoding a multimeraccording to the invention, wherein the separate nucleic acids encodingeach unit may have homologous or heterologous DNA sequences.

In a fourth aspect the present invention discloses an expression system,which comprises, a nucleic acid or a vector as disclosed above. Theexpression system may e.g. be a gram-positive or gram-negativeprokaryotic host cell system, e.g. E.coli or Bacillus sp. which has beenmodified to express the present polypeptide or multimer. In analternative embodiment, the expression system is a eukaryotic host cellsystem, such as a yeast, e.g. Pichia pastoris or Saccharomycescerevisiae, or mammalian cells, e.g. CHO cells.

In a fifth aspect, the present invention discloses a separation matrix,wherein a plurality of polypeptides or multimers according to anyembodiment disclosed above have been coupled to a solid support. Theseparation matrix may comprise at least 11, such as 11-21, 15-21 or15-18 mg/ml Fc-binding ligands covalently coupled to a porous support,wherein:

-   a) the ligands comprise multimers of alkali-stabilized Protein A    domains,-   b) the porous support comprises cross-linked polymer particles    having a volume-weighted median diameter (d50,v) of 56-70, such as    56-66, micrometers and a dry solids weight of 55-80, such as 60-78    or 65-78, mg/ml. The cross-linked polymer particles may further have    a pore size corresponding to an inverse gel filtration    chromatography Kd value of 0.69-0.85, such as 0.70-0.85 or    0.69-0.80, for dextran of Mw 110 kDa. Suitably, the cross-linked    polymer particles can have a high rigidity, to be able to withstand    high flow rates. The rigidity can be measured with a pressure-flow    test as further described in Example 8, where a column packed with    the matrix is subjected to increasing flow rates of distilled water.    The pressure is increased stepwise and the flow rate and back    pressure measured, until the flow rate starts to decrease with    increasing pressures. The maximum flow rate achieved and the maximum    pressure (the back pressure corresponding to the maximum flow rate)    are measured and used as measures of the rigidity. When measured in    a FINELINE 35 column (GE Healthcare Life Sciences) at a bed height    of 300 +/−10 mm, the max pressure can suitably be at least 0.58 MPa,    such as at least 0.60 MPa. This allows for the use of smaller    particle diameters, which is beneficial for the dynamic capacity.    The multimers may e.g. comprise tetramers, pentamers, hexamers or    heptamers of alkali-stabilized Protein A domains, such as hexamers    of alkali-stabilized Protein A domains. The combination of the high    ligand contents with the particle size range, the dry solids weight    range and the optional Kd range provides for a high binding    capacity, e.g. such that the 10% breakthrough dynamic binding    capacity for IgG is at least 45 mg/ml, such as at least 50 or at    least 55 mg/ml at 2.4 min residence time. Alternatively, or    additionally, the 10% breakthrough dynamic binding capacity for IgG    may be at least 60 mg/ml, such as at least 65, at least 70 or at    least 75 mg/ml at 6 min residence time.

The alkali-stabilized Protein A multimers are highly selective for IgGand the separation matrix can suitably have a dissociation constant forhuman IgG2 of below 0.2 mg/ml, such as below 0.1 mg/ml, in 20 mMphosphate buffer, 180 mM NaCl, pH 7.5. This can be determined accordingto the adsorption isotherm method described in N Pakiman et al: J ApplSci 12, 1136-1141 (2012).

In certain embodiments the alkali-stabilized Protein A domains comprisemutants of a parental Fc-binding domain of Staphylococcus Protein A(SpA), as defined by, or having at least 80% such as at least 90%, 95%or 98% identity to, SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO: 5, SEQ ID NO:6, SEQ ID NO:7, SEQ ID NO:22, SEQ ID NO:51 orSEQ ID NO:52, wherein at least the asparagine or serine residue at theposition corresponding to position 11 in SEQ ID NO:4-7 has been mutatedto an amino acid selected from the group consisting of glutamic acid,lysine, tyrosine, threonine, phenylalanine, leucine, isoleucine,tryptophan, methionine, valine, alanine, histidine and arginine, such asan amino acid selected from the group consisting of glutamic acid andlysine. The amino acid residue at the position corresponding to position40 in SEQ ID NO:4-7 may further be, or be mutated to, a valine. Thealkali-stabilized Protein A domains may also comprise any mutations asdescribed in the polypeptide and/or multimer embodiments above.

In some embodiments the alkali-stabilized Protein A domains comprise anFc-binding polypeptide having an amino acid sequence as defined by, orhaving at least 80% or at least 90, 95% or 98% identity to SEQ ID NO:53.

(SEQ ID NO: 53) X₁Q X₂AFYEILX₃LP NLTEEQRX₄X₅F IX₆X₇LKDX₈PSX₉SX₁₀X₁₁X₁₂LAEAKX₁₃ X14NX₁₅AQwherein individually of each other:

-   -   X₁=A or Q or is deleted    -   X₂=E,K,Y,T,F,L,W,I,M,V,A,H or R    -   X₃=H or K    -   X₄=A or N    -   X₅=A, G, S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K    -   X₆=Q or E    -   X₇=S or K    -   X₈=E or D    -   X₉=Q or V or is deleted    -   X₁₀=K,R or A or is deleted    -   X₁₁=A,E or N or is deleted    -   X₁₂=I or L    -   X₁₃=K or R    -   X₁₄=L or Y    -   X₁₅=D, F,Y,W,K or R

In some embodiments, the amino acid residues may individually of eachother be:

-   a) X₁=A or is deleted, X₂=E, X₃=H, X₄=N, X₆=Q, X₇=S, X₈=D, X₉=V or    is deleted, X₁₀=K or is deleted, X₁₁=A or is deleted, X₁₂=I, X₁₃=K,    X₁₄=L.-   b) X₁=A, X₂=E, X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K,    X₁₁=A, X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.-   c) X₁ is A, X₂=E, X₃=H, X₄=N, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁=A,    X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D or-   d) X₁ is A, X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁=A,    X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.

In certain embodiments the invention discloses a separation matrixcomprising at least 15, such as 15-21 or 15-18 mg/ml Fc-binding ligandscovalently coupled to a porous support, wherein the ligands comprisemultimers of alkali-stabilized Protein A domains. These multimers cansuitably be as disclosed in any of the embodiments described above or asspecified below.

Such a matrix is useful for separation of immunoglobulins or otherFc-containing proteins and, due to the improved alkali stability of thepolypeptides/multimers, the matrix will withstand highly alkalineconditions during cleaning, which is essential for long-term repeateduse in a bioprocess separation setting. The alkali stability of thematrix can be assessed by measuring the immunoglobulin-binding capacity,typically using polyclonal human IgG, before and after incubation inalkaline solutions at a specified temperature, e.g. 22 +/−2° C. Theincubation can e.g. be performed in 0.5 M or 1.0 M NaOH for a number of15 min cycles, such as 100, 200 or 300 cycles, corresponding to a totalincubation time of 25, 50 or 75 h. The IgG capacity of the matrix after96-100 15 min incubation cycles or a total incubation time of 24 or 25 hin 0.5 M NaOH at 22 +/−2° C. can be at least 80, such as at least 85, atleast 90 or at least 95% of the IgG capacity before the incubation. Thecapacity of the matrix after a total incubation time of 24 h in 1.0 MNaOH at 22 +/−2° C. can be at least 70, such as at least 80 or at least90% of the IgG capacity before the incubation. The the 10% breakthroughdynamic binding capacity (Qb10%) for IgG at 2.4 min or 6 min residencetime may e.g. be reduced by less than 20% after incubation 31 h in 1.0 Maqueous NaOH at 22 +/−2 C.

As the skilled person will understand, the expressed polypeptide ormultimer should be purified to an appropriate extent before beingimmobilized to a support. Such purification methods are well known inthe field, and the immobilization of protein-based ligands to supportsis easily carried out using standard methods. Suitable methods andsupports will be discussed below in more detail.

The solid support of the matrix according to the invention can be of anysuitable well-known kind. A conventional affinity separation matrix isoften of organic nature and based on polymers that expose a hydrophilicsurface to the aqueous media used, i.e. expose hydroxy (—OH), carboxy(—COOH), carboxamido (—CONH₂, possibly in N- substituted forms),amiNO:(—NH₂, possibly in substituted form), oligo- or polyethylenoxygroups on their external and, if present, also on internal surfaces. Thesolid support can suitably be porous. The porosity can be expressed as aKay or Kd value (the fraction of the pore volume available to a probemolecule of a particular size) measured by inverse size exclusionchromatography, e.g. according to the methods described in GelFiltration Principles and Methods, Pharmacia LKB Biotechnology 1991, pp6-13. Kay is determined as the ratio (V_(e)-V₀)/(V_(t)-V₀), where Ve isthe elution volume of a probe molecule (e.g. Dextran 110 kD), V₀ is thevoid volume of the column (e.g. the elution volume of a high Mw voidmarker, such as raw dextran) and V_(t) is the total volume of thecolumn. Kd can be determined as (V_(e)-V₀)/V_(i), where V_(i) is theelution volume of a salt (e.g. NaCl) able to access all the volumeexcept the matrix volume (the volume occupied by the matrix polymermolecules). By definition, both Kd and Kay values always lie within therange 0-1. The Kay value can advantageously be 0.6-0.95, e.g. 0.7-0.90or 0.6-0.8, as measured with dextran of Mw 110 kDa as a probe molecule.The Kd value as measured with dextran of Mw 110 kDa can suitably be0.68-0.90, such as 0.68-0.85 or 0.70-0.85. An advantage of this is thatthe support has a large fraction of pores able to accommodate both thepolypeptides/multimers of the invention and immunoglobulins binding tothe polypeptides/multimers and to provide mass transport of theimmunoglobulins to and from the binding sites.

The polypeptides or multimers may be attached to the support viaconventional coupling techniques utilising e.g. thiol, amiNO:and/orcarboxy groups present in the ligand. Bisepoxides, epichlorohydrin,CNBr, N-hydroxysuccinimide (NHS) etc are well-known coupling reagents.Between the support and the polypeptide/multimer, a molecule known as aspacer can be introduced, which improves the availability of thepolypeptide/multimer and facilitates the chemical coupling of thepolypeptide/multimer to the support. Depending on the nature of thepolypeptide/multimer and the coupling conditions, the coupling may be amultipoint coupling (e.g. via a plurality of lysines) or a single pointcoupling (e.g. via a single cysteine). Alternatively, thepolypeptide/multimer may be attached to the support by non-covalentbonding, such as physical adsorption or biospecific adsorption.

In some embodiments the matrix comprises 5-25, such as 5-20 mg/ml, 5-15mg/ml, 5-11 mg/ml or 6-11 mg/ml of the polypeptide or multimer coupledto the support. The amount of coupled polypeptide/multimer can becontrolled by the concentration of polypeptide/multimer used in thecoupling process, by the activation and coupling conditions used and/orby the pore structure of the support used. As a general rule theabsolute binding capacity of the matrix increases with the amount ofcoupled polypeptide/multimer, at least up to a point where the poresbecome significantly constricted by the coupled polypeptide/multimer.Without being bound by theory, it appears though that for the Kd valuesrecited for the support, the constriction of the pores by coupled ligandis of lower significance. The relative binding capacity per mg coupledpolypeptide/multimer will decrease at high coupling levels, resulting ina cost-benefit optimum within the ranges specified above.

In certain embodiments the polypeptides or multimers are coupled to thesupport via thioether bonds. Methods for performing such coupling arewell-known in this field and easily performed by the skilled person inthis field using standard techniques and equipment. Thioether bonds areflexible and stable and generally suited for use in affinitychromatography. In particular when the thioether bond is via a terminalor near-terminal cysteine residue on the polypeptide or multimer, themobility of the coupled polypeptide/multimer is enhanced which providesimproved binding capacity and binding kinetics. In some embodiments thepolypeptide/multimer is coupled via a C-terminal cysteine provided onthe protein as described above. This allows for efficient coupling ofthe cysteine thiol to electrophilic groups, e.g. epoxide groups,halohydrin groups etc. on a support, resulting in a thioether bridgecoupling.

In certain embodiments the support comprises a polyhydroxy polymer, suchas a polysaccharide. Examples of polysaccharides include e.g. dextran,starch, cellulose, pullulan, agar, agarose etc. Polysaccharides areinherently hydrophilic with low degrees of nonspecific interactions,they provide a high content of reactive (activatable) hydroxyl groupsand they are generally stable towards alkaline cleaning solutions usedin bioprocessing.

In some embodiments the support comprises agar or agarose. The supportsused in the present invention can easily be prepared according tostandard methods, such as inverse suspension gelation (S Hjertén:Biochim Biophys Acta 79(2), 393-398 (1964). Alternatively, the basematrices are commercially available products, such as crosslinkedagarose beads sold under the name of SEPHAROSE™ FF (GE Healthcare). Inan embodiment, which is especially advantageous for large-scaleseparations, the support has been adapted to increase its rigidity usingthe methods described in U.S. Pat. No. 6,602,990 or U.S. Pat. No.7,396,467, which are hereby incorporated by reference in theirentireties, and hence renders the matrix more suitable for high flowrates.

In certain embodiments the support, such as a polymer, polysaccharide oragarose support, is crosslinked, such as with hydroxyalkyl ether crosslinks. Crosslinker reagents producing such crosslinks can be e.g.epihalohydrins like epichlorohydrin, diepoxides like butanedioldiglycidyl ether, allylating reagents like allyl halides or allylglycidyl ether. Crosslinking is beneficial for the rigidity of thesupport and improves the chemical stability. Hydroxyalkyl ethercrosslinks are alkali stable and do not cause significant nonspecificadsorption.

Alternatively, the solid support is based on synthetic polymers, such aspolyvinyl alcohol, polyhydroxyalkyl acrylates, polyhydroxyalkylmethacrylates, polyacrylamides, polymethacrylamides etc. In case ofhydrophobic polymers, such as matrices based on divinyl andmonovinyl-substituted benzenes, the surface of the matrix is oftenhydrophilised to expose hydrophilic groups as defined above to asurrounding aqueous liquid. Such polymers are easily produced accordingto standard methods, see e.g. “Styrene based polymer supports developedby suspension polymerization” (R Arshady: Chimica e L'Industria 70(9),70-75 (1988)). Alternatively, a commercially available product, such asSOURCE™ (GE Healthcare) is used. In another alternative, the solidsupport according to the invention comprises a support of inorganicnature, e.g. silica, zirconium oxide etc.

In yet another embodiment, the solid support is in another form such asa surface, a chip, capillaries, or a filter (e.g. a membrane or a depthfilter matrix).

As regards the shape of the matrix according to the invention, in oneembodiment the matrix is in the form of a porous monolith. In analternative embodiment, the matrix is in beaded or particle form thatcan be porous or non-porous. Matrices in beaded or particle form can beused as a packed bed or in a suspended form. Suspended forms includethose known as expanded beds and pure suspensions, in which theparticles or beads are free to move. In case of monoliths, packed bedand expanded beds, the separation procedure commonly followsconventional chromatography with a concentration gradient. In case ofpure suspension, batch-wise mode will be used.

In a sixth aspect, the present invention discloses a method of isolatingan immunoglobulin, wherein a separation matrix as disclosed above isused. The method may comprise the steps of:

-   a) contacting a liquid sample comprising an immunoglobulin with a    separation matrix as disclosed above,-   b) washing the separation matrix with a washing liquid,-   c) eluting the immunoglobulin from the separation matrix with an    elution liquid, and-   d) cleaning the separation matrix with a cleaning liquid, which may    comprise 0.1-1.0 M NaOH or KOH, such as 0.4-1.0 M NaOH or KOH.-   Steps a)-d) may be repeated at least 10 times, such as at least 50    times or 50-200 times.

In certain embodiments, the method comprises the steps of:

-   a) contacting a liquid sample comprising an immunoglobulin with a    separation matrix as disclosed above,-   b) washing said separation matrix with a washing liquid,-   c) eluting the immunoglobulin from the separation matrix with an    elution liquid, and-   d) cleaning the separation matrix with a cleaning liquid, which can    alternatively be called a cleaning-in-place (CIP) liquid, e.g. with    a contact (incubation) time of at least 10 min. The method may also    comprise steps of, before step a), providing an affinity separation    matrix according to any of the embodiments described above and    providing a solution comprising an immunoglobulin and at least one    other substance as a liquid sample and of, after step c), recovering    the eluate and optionally subjecting the eluate to further    separation steps, e.g. by anion or cation exchange chromatography,    multimodal chromatography and/or hydrophobic interaction    chromatography. Suitable compositions of the liquid sample, the    washing liquid and the elution liquid, as well as the general    conditions for performing the separation are well known in the art    of affinity chromatography and in particular in the art of Protein A    chromatography. The liquid sample comprising an Fc-containing    protein and at least one other substance may comprise host cell    proteins (HCP), such as CHO cell, E Coli or yeast proteins. Contents    of CHO cell and E Coli proteins can conveniently be determined by    immunoassays directed towards these proteins, e.g. the CHO HCP or E    Coli HCP ELISA kits from Cygnus Technologies. The host cell proteins    or CHO cell/E Coli proteins may be desorbed during step b).

The elution may be performed by using any suitable solution used forelution from Protein A media. This can e.g. be a solution or buffer withpH 5 or lower, such as pH 2.5-5 or 3-5. It can also in some cases be asolution or buffer with pH 11 or higher, such as pH 11-14 or pH 11-13.In some embodiments the elution buffer or the elution buffer gradientcomprises at least one mono- di- or trifunctional carboxylic acid orsalt of such a carboxylic acid.

In certain embodiments the elution buffer or the elution buffer gradientcomprises at least one anion species selected from the group consistingof acetate, citrate, glycine, succinate, phosphate, and formiate.

In some embodiments, the cleaning liquid is alkaline, such as with a pHof 13-14. Such solutions provide efficient cleaning of the matrix, inparticular at the upper end of the interval

In certain embodiments, the cleaning liquid comprises 0.1-2.0 M NaOH orKOH, such as 0.5-2.0 or 0.5-1.0 M NaOH or KOH. These are efficientcleaning solutions, and in particular so when the NaOH or KOHconcentration is above 0.1 M or at least 0.5 M. The high stability ofthe polypeptides of the invention enables the use of such stronglyalkaline solutions.

The method may also include a step of sanitizing the matrix with asanitization liquid, which may e.g. comprise a peroxide, such ashydrogen peroxide and/or a peracid, such as peracetic acid or performicacid.

In some embodiments, steps a)-d) are repeated at least 10 times, such asat least 50 times, 50-200, 50-300 or 50-500 times. This is important forthe process economy in that the matrix can be re-used many times.

Steps a)-c) can also be repeated at least 10 times, such as at least 50times, 50-200, 50-300 or 50-500 times, with step d) being performedafter a plurality of instances of step c), such that step d) isperformed at least 10 times, such as at least 50 times. Step d) can e.g.be performed every second to twentieth instance of step c).

EXAMPLES Mutagenesis of Protein

Site-directed mutagenesis was performed by a two-step PCR usingoligonucleotides coding for the mutations. As template a plasmidcontaining a single domain of either Z, B or C was used. The PCRfragments were ligated into an E. coli expression vector. DNA sequencingwas used to verify the correct sequence of inserted fragments. To formmultimers of mutants an Acc I site located in the starting codons (GTAGAC) of the B, C or Z domain was used, corresponding to amino acids VD.The vector for the monomeric domain was digested with Acc I andphosphatase treated. Acc I sticky-ends primers were designed, specificfor each variant, and two overlapping PCR products were generated fromeach template. The PCR products were purified and the concentration wasestimated by comparing the PCR products on a 2% agarose gel. Equalamounts of the pair wise PCR products were hybridized (90° C.->25° C. in45min) in ligation buffer. The resulting product consists approximatelyto ¼ of fragments likely to be ligated into an Acc I site (correct PCRfragments and/or the digested vector). After ligation and transformationcolonies were PCR screened to identify constructs containing the desiredmutant. Positive clones were verified by DNA sequencing.

Construct Expression and Purification

The constructs were expressed in the bacterial periplasm by fermentationof E. coli K12 in standard media. After fermentation the cells wereheat-treated to release the periplasm content into the media. Theconstructs released into the medium were recovered by microfiltrationwith a membrane having a 0.2 μm pore size.

Each construct, now in the permeate from the filtration step, waspurified by affinity. The permeate was loaded onto a chromatographymedium containing immobilized IgG (IgG Sepharose 6FF, GE Healthcare).The loaded product was washed with phosphate buffered saline and elutedby lowering the pH.

The elution pool was adjusted to a neutral pH (pH 8) and reduced byaddition of dithiothreitol. The sample was then loaded onto an anionexchanger. After a wash step the construct was eluted in a NaCl gradientto separate it from any contaminants. The elution pool was concentratedby ultrafiltration to 40-50 mg/ml. It should be noted that thesuccessful affinity purification of a construct on an immobilized IgGmedium indicates that the construct in question has a high affinity toIgG.

The purified ligands were analyzed with RPC LC-MS to determine thepurity and to ascertain that the molecular weight corresponded to theexpected (based on the amino acid sequence).

Example 1

The purified monomeric ligands listed in Table 1, further comprising forSEQ ID NO:8-16, 23-28 and 36-48 an AQGT leader sequence at theN-terminus and a cysteine at the C terminus, were immobilized on BiacoreCM5 sensor chips (GE Healthcare, Sweden), using the amine coupling kitof GE Healthcare (for carbodiimide coupling of amines on thecarboxymethyl groups on the chip) in an amount sufficient to give asignal strength of about 200-1500 RU in a Biacore surface plasmonresonance (SPR) instrument (GE Healthcare, Sweden) . To follow the IgGbinding capacity of the immobilized surface lmg/ml human polyclonal IgG(Gammanorm) was flowed over the chip and the signal strength(proportional to the amount of binding) was noted. The surface was thencleaned-in-place (CIP), i.e. flushed with 500 mM NaOH for 10 minutes atroom temperature (22 +/−2° C.). This was repeated for 96-100 cycles andthe immobilized ligand alkaline stability was followed as the remainingIgG binding capacity (signal strength) after each cycle. The results areshown in Table 1 and indicate that at least the ligands Zvar(N11K)1,Zvar(N11E)1, Zvar(N11Y)1, Zvar(N11T)1, Zvar(N11F)1, Zvar(N11L)1,Zvar(N11W)1, ZN11I)1, Zvar(N11M)1, Zvar(N11V)1, Zvar(N11A)1,Zvar(N11H1), Zvar(N11R)1, Zvar(N11E,Q32A)1, Zvar(N11E,Q32E,Q40E)1 andZvar(N11E,Q32E,K5OR)1, Zvar(Q9A,N11E,N43A)1, Zvar(Q9A,N11E,N28A,N43A)1,Zvar(Q9A,N11E,Q40V,A42K,N43E,L44I)1,Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)1,Zvar(Q9A,N11E,N28A,Q40V,A42K,N43A,L44I)1,Zvar(N11K,H18K,S33K,D37E,A42R,N43A,L44I, K5OR,L51Y)1,Zvar(Q9A,N11K,H18K,S33K,D37E,A42R,N43A,L44I, K5OR,L51Y)1, Zvar(N11K,H18K, D37E, A42R, N43A, L44I)1, Zvar(Q9A, N11K, H18K, D37E, A42R, N43A,L44I)1 and Zvar(Q9A, N11K, H18K, D37E, A42R, N43A, L44I, K5OR)1, as wellas the varieties of Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)1 havingG,S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K in position 29, the varieties ofZvar(Q9A,N11E,Q40V,A42K,N43A,L44I)1 having F,Y,W,K or R in position 53and the varieties of Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)1 where Q9, Q40,A42 or N43 has been deleted, have an improved alkali stability comparedto the parental structure Zvarl, used as the reference. Further, theligands B(Q9A,N11E,Q40V,A42K,N43A,L44I)1 and C(Q9A,N11E,E43A)1 have animproved stability compared to the parental B and C domains, used asreferences.

TABLE 1 Monomeric ligands, evaluated by Biacore (0.5M NaOH). CapacityReference Capacity after 96-100 capacity after relative to LigandSequence cycles 96- 100 cycles reference Zvar(N11E,Q32A)1 SEQ ID 57% 55%1.036 NO: 12 Zvar(N11E)1 SEQ ID 59% 55% 1.073 NO: 13Zvar(N11E,Q32E,Q40E)1 SEQ ID 52% 51% 1.020 NO: 14 Zvar(N11E,Q32E,K50R)1SEQ ID 53% 51% 1.039 NO: 15 Zvar(N11K)1 SEQ ID 62% 49% 1.270 NO: 16Zvar(N11Y)1 SEQ ID 55% 46% 1.20 NO: 38 Zvar(N11T)1 SEQ ID 50% 46% 1.09NO: 39 Zvar(N11F)1 SEQ ID 55% 46% 1.20 NO: 40 Zvar(N11L)1 SEQ ID 57% 47%1.21 NO: 41 Zvar(N11W)1 SEQ ID 57% 47% 1.21 NO: 42 Zvar(N11I)1 SEQ ID57% 47% 1.21 NO: 43 Zvar(N11M)1 SEQ ID 58% 46% 1.26 NO: 44 Zvar(N11V)1SEQ ID 56% 46% 1.22 NO: 45 Zvar(N11A)1 SEQ ID 58% 46% 1.26 NO: 46Zvar(N11H)1 SEQ ID 57% 46% 1.24 NO: 47 Zvar(N11R)1 SEQ ID 59% 46% 1.28NO: 48 Zvar(Q9A,N11E,N43A)1 SEQ ID 70% 47% 1.49 NO: 8Zvar(Q9A,N11E,N28A,N43A)1 SEQ ID 68% 47% 1.45 NO: 9Zvar(Q9A,N11E,Q40V,A42K,N43E,L44I)1 SEQ ID 67% 47% 1.43 NO: 10Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)1 SEQ ID 66% 47% 1.40 NO: 11Zvar(Q9A,N11E,N28A,Q40V,A42K,N43A,L44I)1 SEQ ID 65% 48% 1.35 NO: 24Zvar(N11K,H18K,S33K,D37E,A42R,N43A,L44I,K50R,L51Y)1 SEQ ID 67% 46% 1.46NO: 23 Zvar(Q9A,N11K,H18K,S33K,D37E,A42R,N43A,L44I,K50R,L51Y)1 SEQ ID59% 46% 1.28 NO: 25 Zvar(N11K,H18K,D37E,A42R,N43A,L44I)1 SEQ ID 59% 45%1.31 NO: 26 Zvar(Q9A,N11K,H18K,D37E,A42R,N43A,L44I)1 SEQ ID 63% 45% 1.40NO: 27 Zvar(Q9A,N11K,H18K,D37E,A42R,N43A,L44I,K50R)1 SEQ ID 67% 45% 1.49NO: 28 B(Q9A,N11E,Q40V,A42K,N43A,L44I)1 SEQ ID 39% 35% 1.11 NO: 36C(Q9A,N11E,E43A)1 SEQ ID 60% 49% 1.22 NO: 37Zvar(Q9A,N11E,A29G,Q40V,A42K,N43A,L44I)1 SEQ ID 69% 48% 1.44 NO: 54Zvar(Q9A,N11E,A29S,Q40V,A42K,N43A,L44I)1 SEQ ID 66% 48% 1.38 NO: 55Zvar(Q9A,N11E,A29Y,Q40V,A42K,N43A,L44I)1 SEQ ID 61% 48% 1.27 NO: 56Zvar(Q9A,N11E,A29Q,Q40V,A42K,N43A,L44I)1 SEQ ID 60% 47% 1.28 NO: 57Zvar(Q9A,N11E,A29T,Q40V,A42K,N43A,L44I)1 SEQ ID 60% 47% 1.28 NO: 58Zvar(Q9A,N11E,A29N,Q40V,A42K,N43A,L44I)1 SEQ ID 61% 47% 1.30 NO: 59Zvar(Q9A,N11E,A29F,Q40V,A42K,N43A,L44I)1 SEQ ID 62% 46% 1.35 NO: 60Zvar(Q9A,N11E,A29L,Q40V,A42K,N43A,L44I)1 SEQ ID 61% 46% 1.33 NO: 61Zvar(Q9A,N11E,A29W,Q40V,A42K,N43A,L44I)1 SEQ ID 60% 46% 1.30 NO: 62Zvar(Q9A,N11E,A29I,Q40V,A42K,N43A,L44I)1 SEQ ID 58% 47% 1.23 NO: 63Zvar(Q9A,N11E,A29M,Q40V,A42K,N43A,L44I)1 SEQ ID 62% 47% 1.32 NO: 64Zvar(Q9A,N11E,A29V,Q40V,A42K,N43A,L44I)1 SEQ ID 62% 47% 1.32 NO: 65Zvar(Q9A,N11E,A29D,Q40V,A42K,N43A,L44I)1 SEQ ID 56% 47% 1.19 NO: 66Zvar(Q9A,N11E,A29E,Q40V,A42K,N43A,L44I)1 SEQ ID 57% 47% 1.21 NO: 67Zvar(Q9A,N11E,A29H,Q40V,A42K,N43A,L44I)1 SEQ ID 57% 47% 1.21 NO: 68Zvar(Q9A,N11E,A29R,Q40V,A42K,N43A,L44I)1 SEQ ID 58% 46% 1.26 NO: 69Zvar(Q9A,N11E,A29K,Q40V,A42K,N43A,L44I)1 SEQ ID 59% 46% 1.28 NO: 70Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I,D53F)1 SEQ ID 58% 46% 1.26 NO: 71Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I,D53Y)1 SEQ ID 59% 46% 1.28 NO: 72Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I,D53W)1 SEQ ID 62% 46% 1.35 NO: 73Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I,D53K)1 SEQ ID 65% 46% 1.41 NO: 74Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I,D53R)1 SEQ ID 60% 46% 1.30 NO: 75Zvar(Q9del,N11E,Q40V,A42K,N43A,L44I)1 SEQ ID 60% 46% 1.30 NO: 76Zvar(Q9A,N11E,Q40del,A42K,N43A,L44I)1 SEQ ID 59% 46% 1.28 NO: 77Zvar(Q9A,N11E,Q40V,A42del,N43A,L44I)1 SEQ ID 57% 46% 1.24 NO: 78Zvar(Q9A,N11E,Q40V,A42K,N43del,L44I)1 SEQ ID 55% 46% 1.20 NO: 79

The Biacore experiment can also be used to determine the binding anddissociation rates between the ligand and IgG. This was used with theset-up as described above and with an IgG1 monoclonal antibody as probemolecule. For the reference Zvar1, the on-rate (10⁵ M⁻¹s⁻¹) was 3.1 andthe off-rate (10⁵ s⁻¹) was 22.1, giving an affinity (off-rate/on-rate)of 713 pM. For Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)1 (SEQ ID NO:11), theon-rate was 4.1 and the off-rate 43.7, with affinity 1070 pM. The IgGaffinity was thus somewhat higher for the mutated variant.

Example 2

The purified dimeric, tetrameric and hexameric ligands listed in Table 2were immobilized on Biacore CM5 sensor chips (GE Healthcare, Sweden),using the amine coupling kit of GE Healthcare (for carbodiimide couplingof amines on the carboxymethyl groups on the chip) in an amountsufficient to give a signal strength of about 200-1500 RU in a Biacoreinstrument (GE Healthcare, Sweden). To follow the IgG binding capacityof the immobilized surface 1 mg/ml human polyclonal IgG (Gammanorm) wasflowed over the chip and the signal strength (proportional to the amountof binding) was noted. The surface was then cleaned-in-place (CIP), i.e.flushed with 500mM NaOH for 10 minutes at room temperature (22 +/−2°C.). This was repeated for 300 cycles and the immobilized ligandalkaline stability was followed as the remaining IgG binding capacity(signal strength) after each cycle. The results are shown in Table 2 andin FIG. 2 and indicate that at least the ligands Zvar(Q9A,N11E,N43A)4,Zvar(Q9A,N11E,N28A,N43A)4, Zvar(Q9A,N11E,Q40V,A42K,N43E,L44I)4 andZvar(Q9A,N11E,Q40V,A42K,N43A,L44I)4,Zvar(Q9A,N11E,D37E,Q40V,A42K,N43A,L44I)4 andZvar(Q9A,N11E,D37E,Q40V,A42R,N43A,L44I)4 have an improved alkalistability compared to the parental structure Zvar4, which was used as areference. The hexameric ligand Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)6 alsohas improved alkali stability compared to the parental structure Zvar6,used as a reference. Further, Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I) dimerswith deletions of a) D2,A3,K4; b) K58,V1,D2; c) P57,K58,V1,D2,A3; d)K4,F5,D6,K7,E8; e) A56,P57,K58; V1,D2,A3 or f) V1,D2,A3,K4,F5,D6,K7,E8from the linker region between the two monomer units have improvedalkali stability compared to the parental structure Zvar2, used as areference. Also Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I) dimers with aninsertion of YEDG between K58 and V1 in the linker region have improvedalkali stability compared to Zvar2.

TABLE 2 Dimeric, tetrameric and hexameric ligands, evaluated by Biacore(0.5M NaOH). Re- Ca- Re- Ca- Re- Ca- maining pacity maining pacitymaining pacity capacity relative capacity relative capacity relative SEQ100 to ref. 200 to ref. 300 to ref. ID cycles 100 cycles 200 cycles 300Ligand NO: (%) cycles (%) cycles (%) cycles Zvar4 21 67 1 36 1 16 1Zvar(Q9A, N11E, N43A)4 17 81 1.21 62 1.72 41 2.56 Zvar(Q9A, N11E, N28A,18 80 1.19 62 1.72 42 2.62 N43A)4 Zvar(Q9A, N11E, Q40V, 19 84 1.25 651.81 48 3.00 A42K, N43E, L44I)4 Zvar(Q9A, N11E, Q40V, 20 90 1.34 74 2.0657 3.56 A42K, N43A, L44I)4 Zvar(Q9A, N11E, N28A, 32 84 1.24 Not Not NotNot Q40V, A42K, N43A, tested tested tested tested L44I)4 Zvar(Q9A, N11E,Q40V, 33 87 1.30 Not Not Not Not A42K, N43A, L44I)6 tested tested testedtested Zvar(Q9A, N11E, D37E, 34 81 1.13 Not Not Not Not Q40V, A42K,N43A, tested tested tested tested L44I)4 Zvar(Q9A, N11E, D37E, 35 841.17 Not Not Not Not Q40V, A42R, N43A, tested tested tested testedL44I)4 Zvar(Q9A, N11E, Q40V, 80 70 1.27 Not Not Not Not A42K, N43A,L44I)2 with tested tested tested tested D2, A3 and K4 in linker deletedZvar(Q9A, N11E, Q40V, 81 76 1.38 Not Not Not Not A42K, N43A, L44I)2 withtested tested tested tested 1(58, V1 and D2 in linker deleted Zvar(Q9A,N11E, Q40V, 82 74 1.35 Not Not Not Not A42K, N43A, L44I)2 with testedtested tested tested P57, K58, V1, D2 and A3 in linker deleted Zvar(Q9A,N11E, Q40V, 83 70 1.30 Not Not Not Not A42K, N43A, L44I)2 with testedtested tested tested K4, F5, D6, K7 and E8 in linker deleted Zvar(Q9A,N11E, Q40V, 84 68 1.26 Not Not Not Not A42K, N43A, L44I)2 with testedtested tested tested A56, P57 and K58 in linker deleted Zvar(Q9A, N11E,Q40V, 85 75 1.39 Not Not Not Not A42K, N43A, L44I)2 with tested testedtested tested V1, D2 and A3 in linker deleted Zvar(Q9A, N11E, Q40V, 8662 1.13 Not Not Not Not A42K, N43A, L44I)2 with tested tested testedtested V1, D2, A3, K4, F5, D6, K7 and E8 in linker deleted Zvar(Q9A,N11E, Q40V, 87 72 1.31 Not Not Not Not A42K, N43A, L44I)2 with testedtested tested tested YEDG inserted in linker between K58 and V1 Zvar2 8855 1 Not Not Not Not tested tested tested tested

Example 3

Example 2 was repeated with 100 CIP cycles of three ligands using 1 MNaOH instead of 500 mM as in Example 2. The results are shown in Table 3and show that all three ligands have an improved alkali stability alsoin 1M NaOH, compared to the parental structure Zvar4 which was used as areference.

TABLE 3 Tetrameric ligands, evaluated by Biacore (1M NaOH). RemainingCapacity capacity 100 relative to Ligand Sequence cycles (%) ref. 100cycles Zvar4 SEQ ID NO: 21 27 1 Zvar(Q9A,N11E,N28A,N43A)4 SEQ ID NO: 1855 2.04 Zvar(Q9A,N11E,Q40V,A42K,N43E,L44I)4 SEQ ID NO: 19 54 2.00Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)4 SEQ ID NO: 20 56 2.07

Example 4

The purified tetrameric ligands of Table 2 (all with an additionalN-terminal cysteine) were immobilized on agarose beads using the methodsdescribed below and assessed for capacity and stability. The results areshown in Table 4 and FIG. 3.

TABLE 4 Matrices with tetrametric ligands, evaluated in columns (0.5MNaOH). Remaining Remaining Capacity Initial IgG IgG capacity IgGcapacity retention SEQ Ligand capacity Qb10 after six after six relativeto ID content Qb10 4 h cycles 4 h cycles ref. after six Ligand NO.(mg/ml) (mg/ml) (mg/ml) (%) 4 h cycles Zvar4 21 7 52.5 36.5 60 1 Zvar421 12 61.1 43.4 71 1 Zvar(Q9A,N11E,N28A,N43A)4 18 7.0 49.1 44.1 90 1.50Zvar(Q9A,N11E,N28A,N43A)4 18 12.1 50.0 46.2 93 1.31Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)4 20 7.2 49.0 44.2 90 1.50Zvar(Q9A,N11E,Q40V,A42K,N43A,L44I)4 20 12.8 56.3 53.6 95 1.34Zvar(N11K,H18K,S33K,D37E,A42R,N43A, 30 9.7 56.3 52.0 92 1.53L44I,K50R,L51Y)4 Zvar(Q9A,N11K,H18K,D37E,A42R)4 31 10.8 56.9 52.5 921.30

Activation

The base matrix used was rigid cross-linked agarose beads of 85micrometers (volume-weighted, d50V) median diameter, prepared accordingto the methods of U.S. Pat. No. 6,602,990, hereby incorporated byreference in its entirety, and with a pore size corresponding to aninverse gel filtration chromatography Kay value of 0.70 for dextran ofMw 110 kDa, according to the methods described in Gel FiltrationPrinciples and Methods, Pharmacia LKB Biotechnology 1991, pp 6-13.

25 mL (g) of drained base matrix, 10.0 mL distilled water and 2.02 gNaOH (s) was mixed in a 100 mL flask with mechanical stirring for 10 minat 25° C. 4.0 mL of epichlorohydrin was added and the reactionprogressed for 2 hours. The activated gel was washed with 10 gelsediment volumes (GV) of water.

Coupling

To 20 mL of ligand solution (50 mg/mL) in a 50 ml Falcon tube, 169 mgNaHCO₃, 21 mg Na₂CO₃, 175 mg NaCl and 7 mg EDTA, was added. The Falcontube was placed on a roller table for 5-10 min, and then 77 mg of DTEwas added. Reduction proceeded for >45 min. The ligand solution was thendesalted on a PD10 column packed with Sephadex G-25. The ligand contentin the desalted solution was determined by measuring the 276 nm UVabsorption.

The activated gel was washed with 3-5 GV {0.1 M phosphate/1 mM EDTA pH8.6} and the ligand was then coupled according to the method describedin U.S. Pat. No. 6,399,750, hereby incorporated by reference in itsentirety. All buffers used in the experiments had been degassed bynitrogen gas for at least 5-10 min. The ligand content of the gels couldbe controlled by varying the amount and concentration of the ligandsolution.

After immobilization the gels were washed 3×GV with distilled water. Thegels +1 GV {0.1 M phosphate/1 mM EDTA/10% thioglycerol pH 8.6} was mixedand the tubes were left in a shaking table at room temperatureovernight. The gels were then washed alternately with 3×GV {0.1 MTRIS/0.15 M NaCl pH 8.6} and 0.5 M HAc and then 8-10×GV with distilledwater. Gel samples were sent to an external laboratory for amino acidanalysis and the ligand content (mg/ml gel) was calculated from thetotal amino acid content.

Protein

Gammanorm 165 mg/ml (Octapharma), diluted to 2 mg/ml in Equilibrationbuffer.

Equilibration Buffer

PBS Phosphate buffer 10 mM+0.14 M NaCl+0.0027 M KCl, pH 7,4 (Medicago)

Adsorption Buffer

PBS Phosphate buffer 10 mM+0.14 M NaCl+0.0027 M KCl, pH 7,4 (Medicago)

Elution Buffers

100 mM acetate pH 2.9

Dynamic Binding Capacity

2 ml of resin was packed in TRICORN™ 5 100 columns. The breakthroughcapacity was determined with an AKTAExplorer 10 system at a residencetime of 6 minutes (0.33 ml/min flow rate). Equilibration buffer was runthrough the bypass column until a stable baseline was obtained. This wasdone prior to auto zeroing. Sample was applied to the column until a100% UV signal was obtained. Then, equilibration buffer was appliedagain until a stable baseline was obtained.

Sample was loaded onto the column until a UV signal of 85% of maximumabsorbance was reached. The column was then washed with 5 column volumes(CV) equilibration buffer at flow rate 0.5ml/min. The protein was elutedwith 5 CV elution buffer at a flow rate of 0.5 ml/min. Then the columnwas cleaned with 0.5M NaOH at flow rate 0.2 ml/min and re-equilibratedwith equilibration buffer.

For calculation of breakthrough capacity at 10%, the equation below wasused. That is the amount of IgG that is loaded onto the column until theconcentration of IgG in the column effluent is 10% of the IgGconcentration in the feed.

$q_{10\%} = {\frac{C_{0}}{V_{C}}\left\lbrack {V_{app} - V_{sys} - {\int\limits_{V_{sys}}^{V_{app}}{\frac{{A(V)} - A_{sub}}{A_{100\%} - A_{sub}}*dv}}} \right\rbrack}$

-   -   Aim %=100% UV signal;    -   A_(sub)=absorbance contribution from non-binding IgG subclass;    -   A(V) =absorbance at a given applied volume;    -   V_(c)=column volume;    -   V_(app)=volume applied until 10% breakthrough;    -   V_(sys)=system dead volume;    -   C₀=feed concentration.

The dynamic binding capacity (DBC) at 10% breakthrough was calculated.The dynamic binding capacity (DBC) was calculated for 10 and 80%breakthrough.

-   -   CIP−0.5 M NaOH

The 10% breakthrough DBC (Qb10) was determined both before and afterrepeated exposures to alkaline cleaning solutions. Each cycle included aCIP step with 0.5 M NaOH pumped through the column at a rate of 0.5/minfor 20 min, after which the column was left standing for 4 h. Theexposure took place at room temperature (22 +/−2° C.). After thisincubation, the column was washed with equilibration buffer for 20 minat a flow rate of 0.5 ml/min. Table 4 shows the remaining capacity aftersix 4 h cycles (i.e. 24 h cumulative exposure time to 0.5 M NaOH), bothin absolute numbers and relative to the initial capacity.

Example 5

Example 4 was repeated with the tetrameric ligands shown in Table 5, butwith 1.0 M NaOH used in the CIP steps instead of 0.5 M. The results areshown in Table 5 and in FIG. 4.

TABLE 5 Matrices with tetrametric ligands, evaluated in columns 1.0MNaOH. Re- main- Re- ing main- Ca- IgG ing pacity Initial ca- IgG re- IgGpacity ca- tention ca- Qb10 pacity relative pacity after after to ref.SEQ Ligand Qb10 six 4 h six 4 h after ID content (mg/ cycles cycles six4 h Ligand NO. (mg/ml) ml) (mg/ml) (%) cycles Zvar4 21 12 60.1 33.5 56 1Zvar(Q9A, N11E, 20 12.8 60.3 56.0 93 1.67 Q40V, A42K, N43A, L44I)4Zvar(N11K, H18K, 30 9.7 62.1 48.1 77 1.44 S33K, D37E, A42R, N43A, L44I,K50R, L51Y)4

Example 6 Base Matrices

The base matrices used were a set of rigid cross-linked agarose beadsamples of 59-93 micrometers (volume-weighted, d50V) median diameter(determined on a Malvern Mastersizer 2000 laser diffraction instrument),prepared according to the methods of U.S. Pat. No. 6,602,990 and with apore size corresponding to an inverse gel filtration chromatography Kdvalue of 0.62-0.82 for dextran of Mw 110 kDa, according to the methodsdescribed above, using HR10/30 columns (GE Healthcare) packed with theprototypes in 0.2 M NaCl and with a range of dextran fractions as probemolecules (flow rate 0.2 ml/min). The dry weight of the bead samplesranged from 53 to 86 mg/ml, as determined by drying 1.0 ml drainedfilter cake samples at 105 ° C. over night and weighing.

TABLE 6 Base matrix samples Base matrix Kd d50v (μm) Dry weight (mg/ml)A18 0.704 59.0 56.0 A20 0.70 69.2 55.8 A27 0.633 87.2 74.2 A28 0.63867.4 70.2 A29 0.655 92.6 57.5 A32 0.654 73.0 70.5 A33 0.760 73.1 55.5A38 0.657 70.9 56.2 A39 0.654 66.0 79.1 A40 0.687 64.9 74.9 A41 0.70881.7 67.0 A42 0.638 88.0 59.4 A43 0.689 87.5 77.0 A45 0.670 56.6 66.0A52 0.620 53.10 63.70 A53 0.630 52.6 86.0 A54 0.670 61.3 75.3 A55 0.64062.0 69.6 A56 0.740 61.0 56.0 A56-2 0.740 51.0 56.0 A62a 0.788 48.8 70.1A62b 0.823 50.0 46.9 A63a 0.790 66.8 59.6 A63b 0.765 54.0 79.0 A65a0.796 58.0 60.0 A65b 0.805 57.3 46.0 B5 0.793 69.0 84.4 C1 0.699 71.073.4 C2 0.642 66.5 81.1 C3 0.711 62.0 82.0 C4 0.760 62.0 82.0 H31 0.71782.0 59.0 H35 0.710 81.1 61.0 H40 0.650 52.8 65.0 I1 0.640 50.0 67.0 410.702 81.6 60.6 517 0.685 87.9 64.4 106 0.692 86.7 64.6 531C 0.661 51.763.8 P10 0.741 59.3 70.0 S9 0.736 64.1 72.2

Coupling

100 ml base matrix was washed with 10 gel volumes distilled water on aglass filter. The gel was weighed (1 g=1 ml) and mixed with 30 mldistilled water and 8.08 g NaOH (0.202 mol) in a 250 ml flask with anagitator. The temperature was adjusted to 27 +/−2° C. in a water bath.16 ml epichlorohydrin (0.202 mol) was added under vigorous agitation(about 250 rpm) during 90 +/−10 minutes. The reaction was allowed tocontinue for another 80 +/−10 minutes and the gel was then washedwith >10 gel volumes distilled water on a glass filter until neutral pHwas reached. This activated gel was used directly for coupling as below.

To 16.4 mL of ligand solution (50 mg/mL) in a 50 ml Falcon tube, 139 mgNaHCO_(3,) 17.4 mg Na₂CO_(3,) 143.8 mg NaCl and 141 mg EDTA, was added.The Falcon tube was placed on a roller table for 5-10 min, and then 63mg of DTE was added. Reduction proceeded for >45 min. The ligandsolution was then desalted on a PD10 column packed with Sephadex G-25.The ligand content in the desalted solution was determined by measuringthe 276 nm UV absorption.

The activated gel was washed with 3-5 GV {0.1 M phosphate/1 mM EDTA pH8.6} and the ligand was then coupled according to the method describedin U.S. Pat. No. 6,399,750 5.2.2, although with considerably higherligand amounts (see below). All buffers used in the experiments had beendegassed by nitrogen gas for at least 5-10 min. The ligand content ofthe gels was controlled by varying the amount and concentration of theligand solution, adding 5-20 mg ligand per ml gel. The ligand was eithera tetramer (SEQ ID NO:20) or a hexamer (SEQ ID NO:33) of analkali-stabilized mutant.

After immobilization the gels were washed 3×GV with distilled water. Thegels +1 GV {0.1 M phosphate/1 mM EDTA/10% thioglycerol pH 8.6} was mixedand the tubes were left in a shaking table at room temperatureovernight. The gels were then washed alternately with 3×GV {0.1 MTRIS/0.15 M NaCl pH 8.6} and 0.5 M HAc and then 8-10×GV with distilledwater. Gel samples were sent to an external laboratory for amino acidanalysis and the ligand content (mg/ml gel) was calculated from thetotal amino acid content.

Evaluation

The Qb10% dynamic capacity for polyclonal human IgG at 2.4 and 6 minresidence time was determined as outlined in Example 4.

TABLE 7 Prototype results Ligand Base content Qb10% 2.4 Qb10% 6Prototype matrix (mg/ml) Multimer min (mg/ml) min (mg/ml) N1 A38 7.45tetramer 44.4 58.25 N2 A20 7.3 tetramer 45.12 57.21 N3 A42 6.72 tetramer33.56 50.02 N4 A29 7.3 tetramer 36.34 51.8 N5 A28 7.9 tetramer 42.3858.25 N6 A39 6.96 tetramer 41.88 54.67 N7 A27 7.5 tetramer 29.19 48.73N8 A43 6.99 tetramer 33.43 49.79 N9 A38 11.34 tetramer 48.1 72.78 N10A20 10.6 tetramer 50.66 70.07 N11 A42 11.1 tetramer 32.25 57.78 N12 A2911 tetramer 34.85 64.68 N13 A28 11.9 tetramer 39.92 63.75 N14 A39 10.48tetramer 44.37 64.79 N15 A27 12.1 tetramer 24.8 55.56 N16 A43 10.51tetramer 31.82 58.04 N17 A41 8.83 tetramer 38.5 56.8 N18 A41 8.83tetramer 37.84 58.6 N19 A41 8.83 tetramer 35.06 57.23 N20 A41 5.0tetramer 35.64 46.04 N21 A41 13.0 tetramer 34.95 62.23 N22 A40 13.15tetramer 56.85 71.09 N23 A33 7.33 tetramer 48.69 55.76 N24 A40 11.03tetramer 54.96 73.8 033A A38 7.5 tetramer 44 58 033B A38 11.3 tetramer48 73 097A A20 7.3 tetramer 45 57 097B A20 10.6 tetramer 51 70 003A A287.9 tetramer 42 58 003B A28 11.9 tetramer 40 64 003C A28 15.8 tetramer37 67 038A A39 7.0 tetramer 42 55 038B A39 10.5 tetramer 44 65 074 A4013.2 tetramer 57 71 093 A33 7.3 tetramer 49 56 058A A40 11.0 tetramer 5574 077 A18 8.2 tetramer 52 59 010 A32 10.7 tetramer 40 57 099 A32 13.3tetramer 37 66 030A B5 6.3 tetramer 32 38 030B B5 9.6 tetramer 45 47293A C1 5.4 tetramer 38 47 293B C1 10.8 tetramer 43 60 294A C2 5.1tetramer 39 46 294B C2 10.5 tetramer 42 57 336A H40 5.6 tetramer 47 52336B H40 9.1 tetramer 52 67 091 A18 13.4 tetramer N/A 63 092 A20 12.8tetramer 49 67 080 A33 9.4 tetramer 51 58 089 A40 6.1 tetramer 49 59688A A62a 6.6 tetramer 41 46 688B A62a 14.8 tetramer 55 62 871 A62a 9.7tetramer 48 60 934A A63a 6.6 tetramer 40 44 934B A63a 14.0 tetramer 4856 017B A65a 13.1 tetramer 56 64 041A A62b 5.2 tetramer 40 N/A 041B A62b11.1 tetramer 52 N/A 116A A65b 5.8 tetramer 42 46 116B A65b 8.8 tetramer49 56 017A A65a 6.1 tetramer 40 44 387A A62a 6.4 tetramer 43 45 387BA62a 7.5 tetramer 47 56 432 A63a 6.1 tetramer 39 44 433A A65a 6.6tetramer 42 47 433B A65a 13.6 tetramer 52 61 579A I1 6.1 tetramer 45 51579B I1 11.2 tetramer 57 68 064A C3 5.9 tetramer 44 52 064B C3 9.0tetramer 49 62 064C C3 14.3 tetramer 51 70 352A C4 10.1 tetramer 55 63352B C4 14.4 tetramer 59 67 066A C3 6.8 hexamer 48 59 066B C3 11.9hexamer 51 73 066C C3 15.1 hexamer 43 61 353A C4 11.2 hexamer 62 74 353BC4 15.2 hexamer 57 82 872A A62a 9.6 hexamer 56 72 872B A62a 14.5 hexamer62 84 869A H40 6.9 hexamer 50 56 869B H40 14.3 hexamer 56 75 869C H4023.0 hexamer 41 65 962A H35 6.8 hexamer 36 49 962B H35 12.3 hexamer 3154 962C H35 20.3 hexamer 20 43 112A A56 7.9 hexamer 47 55 112B A56 12.4hexamer 57 73 112C A56 19.2 hexamer 55 80 113A A56 7.1 hexamer 48 57113B A56 12.4 hexamer 53 73 113C A56 15.2 hexamer 48 76 212A H31 6.5hexamer 37 38 212B H31 10.4 hexamer 50 61 212C H31 20.0 hexamer 31 52213A A33 6.5 hexamer 44 53 213B A33 10.9 hexamer 50 65 213C A33 11.1hexamer 50 68 432A A20 6.4 hexamer 41 56 432B A20 12.4 hexamer 38 64432C A20 21.1 hexamer 44 43 433A A38 5.9 hexamer 47 57 433B A38 11.6hexamer 48 72 433C A38 15.8 hexamer 36 62 742A A54 6.7 hexamer 38 46742B A54 12.6 hexamer 45 52 742C A54 21.1 hexamer 38 65 726A A63b 6.4hexamer 42 46 726B A63b 10.6 hexamer 49 60 726C A63b 16.7 hexamer 53 69793A A56-2 6.8 hexamer 50 58 793B A56-2 12.5 hexamer 59 72 793C A56-219.2 hexamer 61 82 517 517 12.0 tetramer* 35 56 106 106 5.8 tetramer* 3345 531C 531C 11.2 tetramer* 54 65 P10 P10 19.0 hexamer 76 S9 S9 18.4hexamer 56 75 *SEQ ID NO: 21

Example 7

A series of prototypes, prepared as above, with different ligand content(tetramer, SEQ ID NO:20) were incubated in 1 M NaOH for 4, 8 and 31hours at 22 +/−2° C. and the dynamic IgG capacity (Qb10%, 6 minresidence time) was measured before and after incubation. The prototypesare shown in Table 8 and the results in FIGS. 5 and 6. It can be seenthat the stability towards this harsh alkali treatment increases withincreasing ligand content.

TABLE 8 Samples for incubation in 1M NaOH Qb10%, 6 min, before PrototypeLigand content (mg/ml) incubation (mg/ml) N1 12 78 LE28 13 79 N17 16 73N16 20 73

Example 8 Pressure-Flow Testing of Matrices

300 ml sedimented matrix was packed in a FINELINE 35 column (GEHealthcare Life Sciences, Uppsala, Sweden), with 35 mm inner diameterand 330 mm tube height. The gel was suspended in distilled water toproduce a slurry volume of 620 ml and the height of the packed bed was300 +/−10 mm. The packing pressure was 0.10 +/−0.02 bar (10 +/−2 kPa).

Distilled water was then pumped through the column at increasing pumprates and the flow rate (expressed as the linear flow velocity, cm/h)and back pressure (MPa) was measured after 5 min for each pump setting.The measurements were continued until a max flow rate and a max pressurewas reached, i.e. the flow rate and back pressure achieved when the flowrate starts to diminish at increasing back pressures.

TABLE 9 Pressure flow performance of matrices Matrix Max flow velocity,cm/h Max pressure (MPa) 517 1343 0.56 106 1306 0.56 531C 513 0.51 P10862 0.60 S9 1172 0.64

The P10 and S9 matrices have a higher rigidity, as indicated by the maxpressure, and can thus sustain comparatively high flow velocitiesdespite their low (59-64 micrometers) median particle diameters.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims. All patents and patentapplications mentioned in the text are hereby incorporated by referencein their entireties, as if they were individually incorporated.

ITEMIZED LIST OF EMBODIMENTS

-   i. An Fc-binding polypeptide which comprises a sequence as defined    by, or having at least 90% or at least 95% or 98% identity to SEQ ID    NO:53.

(SEQ ID NO: 53) X₁Q X₂AFYEILX₃LP NLTEEQRX₄X₅F IX₆X₇LKDX₈PSX₉SX₁₀X₁₁X₁₂LAEAKX₁₃ X₁₄NX₁₅AQwherein individually of each other:

-   -   X₁=A or Q or is deleted    -   X₂=E,K,Y,T,F,L,W,I,M,V,A,H or R    -   X₃=H or K    -   X₄=A or N    -   X₅=A, G, S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K    -   X₆=Q or E    -   X₇=S or K    -   X₈=E or D    -   X₉=Q or V or is deleted    -   X₁₀=K,R or A or is deleted    -   X₁₁=A,E or N or is deleted    -   X₁₂=I or L    -   X₁₃=K or R    -   X₁₄=L or Y    -   X₁₅=D, F,Y,W,K or R

-   ii. The polypeptide of embodiment i, wherein:    -   X₁=A or is deleted, X₂=E, X₃=H, X₄=N, X₆=Q, X₇=S, X₈=D, X₉=V or        is deleted, X₁₀=K or is deleted, X₁₁=A or is deleted, X₁₂=I,        X₁₃=K, X₁₄=L.

-   iii. The polypeptide of embodiment i or ii, wherein X₁=A, X₂=E,    X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁=A, X₁₂=I,    X₁₃=K, X₁₄=L and X₁₅=D.

-   iv. The polypeptide of embodiment i or ii, wherein Xi is deleted,    X₂=E, X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁=A, X₁₂=I,    X₁₃=K, X₁₄=L and X₁₅=D.

-   v. The polypeptide of embodiment i or ii, wherein X₁=A, X₂=E, X₃=H,    X₄=N, X₅=S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K, X₆=Q, X₇=S, X₈=D, X₉=V,    X₁₀=K, X₁₁=A, X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.

-   vi. The polypeptide of embodiment i or ii, wherein X₁=A, X₂=E, X₃=H,    X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉ is deleted, X₁₀=K, X₁₁=A, X₁₂=I,    X₁₃=K, X₁₄=L and X₁₅=D.

-   vii. The polypeptide of embodiment i or ii, wherein X₁=A, X₂=E,    X₃=H, X₄=N, X₅=A, X₆=Q, X₇=5, X₈=D, X₉=V, X₁₀ is deleted, X₁₁=A,    X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.

-   viii. The polypeptide of embodiment i or ii, wherein X₁=A, X₂=E,    X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁ is deleted,    X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.

-   ix. The polypeptide of embodiment i or ii, wherein X₁=A, X₂=E, X₃=H,    X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K, X₁₁=A, X₁₂=I, X₁₃=K,    X₁₄=L and X₁₅=F,Y,W,K or R.

-   x. An Fc-binding polypeptide comprising a mutant of a parental    Fc-binding domain of Staphylococcus Protein A (SpA), as defined by,    or having at least 90% such as at least 95% or 98% identity to, SEQ    ID NO: 1, SEQ ID NO: 2, SEQ ID NO:3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ    ID NO:6, SEQ ID NO:7, SEQ ID NO:22, SEQ ID NO:51 or SEQ ID NO:52,    wherein at least the asparagine or serine residue at the position    corresponding to position 11 in SEQ ID NO:4-7 has been mutated to an    amino acid selected from the group consisting of glutamic acid,    lysine, tyrosine, threonine, phenylalanine, leucine, isoleucine,    tryptophan, methionine, valine, alanine, histidine and arginine.

-   xi. The polypeptide of embodiment x, comprising a mutant of a    parental Fc-binding domain of Staphylococcus Protein A (SpA), as    defined by, or having at least 90% such as at least 95% or 98%    identity to, SEQ ID NO:51 or SEQ ID NO:52.

-   xii. The polypeptide of embodiment x or xi, wherein the amino acid    residue at the position corresponding to position 11 in SEQ ID    NO:4-7 is a glutamic acid.

-   xiii. The polypeptide of any one of embodiments x-xii, wherein the    amino acid residue at the position corresponding to position 11 in    SEQ ID NO:4-7 is a lysine.

-   xiv. The polypeptide of any one of embodiments x-xiii, wherein the    amino acid residue at the position corresponding to position 29 in    SEQ ID NO:4-7 is a glycine, serine, tyrosine, glutamine, threonine,    asparagine, phenylalanine, leucine, tryptophan, isoleucine,    methionine, valine, aspartic acid, glutamic acid, histidine,    arginine or lysine.

-   xv. The polypeptide of any one of embodiments x-xiv, wherein the    amino acid residue at the position corresponding to position 9 in    SEQ ID NO:4-7 is an alanine.

-   xvi. The polypeptide of any one of embodiments x-xv, wherein the    amino acid residue at the position corresponding to position 9 in    SEQ ID NO:4-7 has been deleted.

-   xvii. The polypeptide of any one of embodiments x-xvi, wherein the    amino acid residue at the position corresponding to position 50 in    SEQ ID NO:4-7 is an arginine or a glutamic acid, such as an    arginine.

-   xviii. The polypeptide of any one of embodiments x-xvii, wherein the    amino acid residue at the position corresponding to position 43 in    SEQ ID NO:4-7 has been deleted.

-   xix. The polypeptide of any one of embodiments x-xviii, wherein the    amino acid residue at the position corresponding to position 28 in    SEQ ID NO:4-7 is an alanine or an asparagine.

-   xx. The polypeptide of any one of embodiments x-xix, wherein the    amino acid residue at the position corresponding to position 40 in    SEQ ID NO:4-7 is selected from the group consisting of asparagine,    alanine, glutamic acid and valine.

-   xxi. The polypeptide of any one of embodiments x-xx, wherein the    amino acid residue at the position corresponding to position 40 in    SEQ ID NO:4-7 has been deleted.

-   xxii. The polypeptide according to any one of embodiments x-xxi,    wherein the amino acid residue at the position corresponding to    position 42 in SEQ ID NO:4-7 is an alanine, lysine or arginine, such    as an arginine.

-   xxiii. The polypeptide according to any one of embodiments x-xxii,    wherein the amino acid residue at the position corresponding to    position 42 in SEQ ID NO:4-7 has been deleted.

-   xxiv. The polypeptide according to any one of embodiments x-xxiii,    wherein the amino acid residue at the position corresponding to    position 44 in SEQ ID NO:4-7 is a leucine or an isoleucine, such as    an isoleucine.

-   xxv. The polypeptide according to any one of embodiments x-xxiv,    wherein the amino acid residue at the position corresponding to    position 44 in SEQ ID NO:4-7 has been deleted.

-   xxvi. The polypeptide according to any one of embodiments x-xxv,    wherein the amino acid residue at the position corresponding to    position 53 in SEQ ID NO:4-7 is a phenylalanine, a tyrosine, a    tryptophan, an arginine or a lysine.

-   xxvii. The polypeptide according to any one of embodiments x-xxvi,    wherein the amino acid residue at the position corresponding to    position 18 in SEQ ID NO:4-7 is a lysine or a histidine, such as a    lysine.

-   xxviii. The polypeptide according to any one of embodiments x-xxvii,    wherein the amino acid residue at the position corresponding to    position 33 in SEQ ID NO:4-7 is a lysine or a serine, such as a    lysine.

-   xxix. The polypeptide according to any one of embodiments x-xxviii,    wherein the amino acid residue at the position corresponding to    position 37 in SEQ ID NO:4-7 is a glutamic acid or an aspartic acid,    such as a glutamic acid.

-   xxx. The polypeptide according to any one of embodiments x-xxix,    wherein the amino acid residue at the position corresponding to    position 51 in SEQ ID NO:4-7 is a tyrosine or a leucine, such as a    tyrosine.

-   xxxi. The polypeptide according to any one of embodiments x-xxx,    wherein one or more of the amino acid residues at the positions    corresponding to positions 1, 2, 3, 4, 5, 6, 7, 8, 56, 57 or 58 in    SEQ ID NO: 4-7 have been deleted.

-   xxxii. The polypeptide according to any one of embodiments x-xxxi,    wherein the mutation is selected from the group consisting of:    -   Q9A,N11E, A29G,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29S,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29Y,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29Q,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29T,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29N,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29F,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29L,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29W,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29I,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29M,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29V,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29D,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29E,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29H,Q40V,A42K,N43A,L44I;    -   Q9A,N11E, A29R,Q40V,A42K,N43A,L44I; and    -   Q9A,N11E, A29K,Q40V,A42K,N43A,L44I.

-   xxxiii. The polypeptide according to any one of embodiments x-xxxii,    wherein the mutation is selected from the group consisting of:    -   Q9A,N11E, Q40V,A42K,N43A,L44I,D53F;    -   Q9A,N11E, Q40V,A42K,N43A,L44I,D53Y;    -   Q9A,N11E, Q40V,A42K,N43A,L44I,D53W;    -   Q9A,N11E, Q40V,A42K,N43A,L44I,D53K; and    -   Q9A,N11E, Q40V,A42K,N43A,L44I,D53R.

-   xxxiv. The polypeptide according to any one of embodiments x-xxxiii,    wherein the mutation is selected from the group consisting of:    -   Q9del,N11E, Q40V,A42K,N43A,L44I;    -   Q9A,N11E, Q40del,A42K,N43A,L44I;    -   Q9A,N11E, Q40V,A42del,N43A,L44I; and    -   Q9A,N11E, Q40V,A42K,N43del,L44I.

-   xxxv. The polypeptide according to any one of embodiments x-xxxiv,    wherein the mutation is selected from the group consisting of:    -   D2del,A3del,K4del,Q9A,N11E,Q40V,A42K,N43A,L44I;    -   V1del,D2del,Q9A,N11E,Q40V,A42K,N43A,L44I,K58del;    -   V1del,D2del,A3del,Q9A,N11E,Q40V,A42K,N43A,L44I,P57del,K58del;    -   K4del,F5del,D6del,K7del,E8del,Q9A,N11E,Q40V,A42K,N43A,L44I;    -   Q9A,N11E,Q40V,A42K,N43A,L44I,A56del,P57del,K58del;    -   V1del,D2del,A3del,Q9A,N11E,Q40V,A42K,N43A,L44I;    -   V1del,D2del,A3del,K4del,F5del,D6del,K7del,E8del,Q9A,N11E,Q40V,A42K,N43A,L44I;and    -   Q9A,N11E,Q40V,A42K,N43A,L44I,K58 insYEDG.

-   xxxvi. The polypeptide according to any one of embodiments i-xxxi,    comprising or consisting essentially of a sequence having at least    90% identity to an amino acid sequence selected from the group    consisting of: SEQ ID NO:54, SEQ ID NO:55, SEQ ID NO:56, SEQ ID    NO:57, SEQ ID NO:58, SEQ ID NO:59, SEQ ID NO:60, SEQ ID NO:61, SEQ    ID NO:62, SEQ ID NO:63, SEQ ID NO:64, SEQ ID NO:65, SEQ ID NO:66,    SEQ ID NO:67, SEQ ID NO:68, SEQ ID NO:69 and SEQ ID NO:70.

-   xxxvii. The polypeptide according to any one of embodiments i-xxxi,    comprising or consisting essentially of a sequence having at least    90% identity to an amino acid sequence selected from the group    consisting of: SEQ ID NO:71, SEQ ID NO:72, SEQ ID NO:73, SEQ ID    NO:74 and SEQ ID NO:75.

-   xxxviii. The polypeptide according to any one of embodiments i-xxxi,    comprising or consisting essentially of a sequence having at least    90% identity to an amino acid sequence selected from the group    consisting of: SEQ ID NO:76, SEQ ID NO:77, SEQ ID NO:78 and SEQ ID    NO:79.

-   xxxix. The polypeptide according to any one of embodiments i-xxxi,    comprising or consisting essentially of a sequence having at least    90% identity to an amino acid sequence selected from the group    consisting of: SEQ ID NO:89, SEQ ID NO:90, SEQ ID NO:91, SEQ ID    NO:92, SEQ ID NO:93, SEQ ID NO:94 and SEQ ID NO:95.

-   xl. The polypeptide according to any preceding embodiment, which    polypeptide has an improved alkaline stability compared to a    polypeptide as defined by SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ    ID NO:4, SEQ ID NO:5, SEQ ID NO:6 or SEQ ID NO:7, such as by SEQ ID    NO:7.

-   xli. The polypeptide according to any preceding embodiment, which    polypeptide has an improved alkaline stability compared to a    parental polypeptide as defined by SEQ ID NO:1, SEQ ID NO:2, SEQ ID    NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6 or SEQ ID NO:7, such as    by SEQ ID NO:7.

-   xlii. The polypeptide according to embodiment xl or xli, wherein the    alkaline stability is improved as measured by the remaining    IgG-binding capacity, after 24, 25 h incubation in 0.5 M or 1.0 M    aqueous NaOH at 22 +/−2° C.

-   xliii. A multimer comprising or consisting essentially of a    plurality of polypeptides as defined by any preceding embodiment.

-   xliv. The multimer according to embodiment xliii, wherein the    polypeptides are linked by linkers comprising up to 25 amino acids,    such as 3-25 or 3-20 amino acids.

-   xlv. The multimer of embodiment xliii or xliv, wherein at least two    polypeptides are linked by linkers comprising or consisting    essentially of a sequence having at least 90% identity with an amino    acid sequence selected from the group consisting of APKVDAKFDKE (SEQ    ID NO:96), APKVDNKFNKE (SEQ ID NO:97), APKADNKFNKE (SEQ ID NO:98),    APKVFDKE (SEQ ID NO:99), APAKFDKE (SEQ ID NO:100), AKFDKE (SEQ ID    NO:101), APKVDA (SEQ ID NO:102), VDAKFDKE (SEQ ID NO:103), APKKFDKE    (SEQ ID NO:104), APK, APKYEDGVDAKFDKE (SEQ ID NO:105) and YEDG (SEQ    ID NO:106).

-   xlvi. The multimer according to embodiment xliv or xlv, which is a    dimer, trimer, tetramer, pentamer, hexamer, heptamer, octamer or    nonamer.

-   xlvii. The multimer according to any one of embodiments xliv-xlvi,    which comprises or consists essentially of a sequence selected from    the group of sequences defined by SEQ ID NO:80, SEQ ID NO:81, SEQ ID    NO:82, SEQ ID NO:83, SEQ ID NO:84, SEQ ID NO:85, SEQ ID NO:86 and    SEQ ID NO:87.

-   xlviii. The polypeptide or multimer according to any preceding    embodiment, further comprising at, or within 1-5 amino acid residues    from, the C-terminal or N-terminal one or more coupling element,    selected from the group consisting of one or more cysteine residues,    a plurality of lysine residues and a plurality of histidine    residues.

-   xlix. A nucleic acid or a vector encoding a polypeptide or multimer    according to any preceding embodiment.    1. An expression system, which comprises a nucleic acid or vector    according to embodiment xlix.

-   li. A separation matrix, wherein a plurality of polypeptides or    multimers according to any one of embodiment i-xlviii have been    coupled to a solid support.

-   lii. A separation matrix comprising at least 11 mg/ml Fc-binding    ligands covalently coupled to a porous support, wherein:    -   a) said ligands comprise multimers of alkali-stabilized Protein        A domains,    -   b) said porous support comprises cross-linked polymer particles        having a volume-weighted median diameter (d50,v) of 55-70        micrometers and a dry solids weight of 55-80 mg/ml.

-   liii. A separation matrix comprising at least 15, such as 15-21 or    15-18 mg/ml Fc-binding ligands covalently coupled to a porous    support, wherein said ligands comprise multimers of    alkali-stabilized Protein A domains.

-   liv. The separation matrix of embodiment li or liii, wherein said    cross-linked polymer particles comprise cross-linked polysaccharide    particles.

-   lv. The separation matrix of any one of embodiments li-liv, wherein    said cross-linked polymer particles comprise cross-linked agarose    particles.

-   lvi. The separation matrix of any one of embodiments li-lv, wherein    said cross-linked polymer particles have a pore size corresponding    to an inverse gel filtration chromatography Kd value of 0.70-0.85    for dextran of Mw 110 kDa.

-   lvii. The separation matrix of any one of embodiments li-lvi, which    has a max pressure of at least 0.58, such as at least 0.60, MPa when    packed at 300 +/−10 mm bed height in a FINELINE 35 column.

-   lviii. The separation matrix of any one of embodiments li-lvii,    wherein said multimers comprise tetramers, pentamers, hexamers or    heptamers of alkali-stabilized Protein A domains.

-   lix. The separation matrix of any one of embodiments li-lviii,    wherein said multimers comprise hexamers of alkali-stabilized    Protein A domains.

-   lx. The separation matrix of any one of embodiments li-lix, wherein    the polypeptides are linked by linkers comprising up to 25 amino    acids, such as 3-25 or 3-20 amino acids.

-   lxi. The separation matrix of any one of embodiments li-lx, wherein    at least two polypeptides are linked by linkers comprising or    consisting essentially of a sequence having at least 90% identity    with an amino acid sequence selected from the group consisting of    APKVDAKFDKE (SEQ ID NO:96), APKVDNKFNKE (SEQ ID NO:97), APKADNKFNKE    (SEQ ID NO:98), APKVFDKE (SEQ ID NO:99), APAKFDKE (SEQ ID NO:100),    AKFDKE (SEQ ID NO:101), APKVDA (SEQ ID NO:102), VDAKFDKE (SEQ ID    NO:103), APKKFDKE (SEQ ID NO:104), APK, APKYEDGVDAKFDKE (SEQ ID    NO:105) and YEDG (SEQ ID NO:106).

-   lxii. The separation matrix of any one of embodiments li-lxi, having    a 10% breakthrough dynamic binding capacity for IgG of at least 45    mg/ml, such as at least 50 or at least 55 mg/ml mg/ml at 2.4 min    residence time.

-   lxiii. The separation matrix of any one of embodiments li-lxii,    having a 10% breakthrough dynamic binding capacity for IgG of at    least 60 mg/ml, such as at least 65, at least 70 or at least 75    mg/ml at 6 min residence time.

-   lxiv. The separation matrix of any one of embodiments li-lxiii,    wherein the 10% breakthrough dynamic binding capacity for IgG at 2.4    or 6 min residence time is reduced by less than 20% after incubation    31 h in 1.0 M aqueous NaOH at 22 +/−2 C.

-   lxv. The separation matrix of any one of embodiments li-lxiv, having    a dissociation constant for IgG2 of below 0.2 mg/ml, such as below    0.1 mg/ml, in 20 mM phosphate buffer, 180 mM NaCl, pH 7.5.

-   lxvi. The separation matrix according to any one of embodiments    li-lxv, wherein the polypeptides or multimers have been coupled to    the solid support or porous support via thioether bonds.

-   lxvii. The separation matrix according to any one of embodiments    li-lxvi, wherein the solid support or porous support is a    polysaccharide.

-   lxviii. The separation matrix according to any one of embodiments    li-lxvii, wherein the IgG capacity of the matrix after 24 incubation    in 0.5 M NaOH at 22 +/−2° C. is at least 80, such as at least 85, at    least 90 or at least 95% of the IgG capacity before the incubation.

-   lxix. The separation matrix according to any one of embodiments    li-lxviii, wherein the IgG capacity of the matrix after 24    incubation in 1.0 M NaOH at 22 +/−2° C. is at least 70, such as at    least 80 or at least 90% of the IgG capacity before the incubation.

-   lxx. The separation matrix of any one of embodiments li-lxix,    wherein said alkali-stabilized Protein A domains or plurality of    polypeptides/multimers comprise(s) mutants of a parental Fc-binding    domain of Staphylococcus Protein A (SpA), as defined by, or having    at least 80% such as at least 90%, 95% or 98% identity to, SEQ ID    NO: 1, SEQ ID NO: 2, SEQ ID NO:3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID    NO:6, SEQ ID NO:7, SEQ ID NO:22, SEQ ID NO:51 or SEQ ID NO:52,    wherein at least the asparagine or serine residue at the position    corresponding to position 11 in SEQ ID NO:4-7 has been mutated to an    amino acid selected from the group consisting of glutamic acid,    lysine, tyrosine, threonine, phenylalanine, leucine, isoleucine,    tryptophan, methionine, valine, alanine, histidine and arginine.

-   lxxi. The separation matrix of embodiment lxx, wherein the amino    acid residue at the position corresponding to position 11 in SEQ ID    NO:4-7 is, or has been mutated to, a glutamic acid or a lysine.

-   lxxii. The separation matrix of embodiment lxx or lxxi, wherein the    amino acid residue at the position corresponding to position 40 in    SEQ ID NO:4-7 is, or has been mutated to, a valine.

-   lxxiii. The separation matrix of any one of embodiments li-lxix,    wherein said alkali-stabilized Protein A domains or plurality of    polypeptides/multimers comprise(s) an Fc-binding polypeptide having    an amino acid sequence as defined by, or having at least 80%, such    as at least 90, 95 or 98%, identity to SEQ ID NO:53.

(SEQ ID NO: 53) X₁Q X₂AFYEILX₃LP NLTEEQRX₄X₅F IX₆X₇LKDX₈PSX₉SX₁₀X₁₁X₁₂LAEAKX₁₃ X₁₄NX₁₅AQwherein individually of each other:

-   -   X₁=A or Q or is deleted    -   X₂=E,K,Y,T,F,L,W,I,M,V,A,H or R    -   X₃=H or K    -   X₄=A or N    -   X₅=A, G, S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K    -   X₆=Q or E    -   X₇=S or K    -   X₈=E or D    -   X₉=Q or V or is deleted    -   X₁₀=K,R or A or is deleted    -   X₁₁=A,E or N or is deleted    -   X₁₂=I or L    -   X₁₃=K or R    -   X₁₄=L or Y    -   X₁₅=D, F,Y,W,K or R

-   lxxiv. The separation matrix of embodiment lxxiiii, wherein    individually of each other:    -   X₁=A or is deleted, X₂=E, X₃=H, X₄=N, X₆=Q, X₇=S, X₈=D, X₉=V or        is deleted, X₁₀=K or is deleted, X₁₁=A or is deleted, X₁₂=I,        X₁₃=K, X₁₄=L.

-   lxxv. The separation matrix of embodiment lxxiii, wherein    individually of each other:    -   X₁=A, X₂=E, X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V, X₁₀=K,        X₁₁=A, X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.

-   lxxvi. The separation matrix of embodiment lxxiii, wherein    individually of each other:    -   wherein X₁ is A, X₂=E, X₃=H, X₄=N, X₆=Q, X₇=S, X₈=D, X₉=V,        X₁₀=K, X₁₁=A, X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.

-   lxxvii. The separation matrix of embodiment lxxiii, wherein    individually of each other:    -   wherein Xi is A, X₃=H, X₄=N, X₅=A, X₆=Q, X₇=S, X₈=D, X₉=V,        X₁₀=K, X₁₁=A, X₁₂=I, X₁₃=K, X₁₄=L and X₁₅=D.

-   lxxviii. The separation matrix according to any one of embodiments    li-lxxvii, wherein said multimers or polypeptides further comprise    at, or within 1-5 amino acid residues from, the C-terminal or    N-terminal one or more coupling element, selected from the group    consisting of one or more cysteine residues, a plurality of lysine    residues and a plurality of histidine residues.

-   lxxix. The separation matrix according to any one of embodiments    li-lxxviii wherein said multimers or polypeptides further comprise    at the N-terminal a leader sequence, comprising 1-20 amino acid    residues.

-   lxxx. A method of isolating an immunoglobulin, wherein a separation    matrix according to any one of embodiments li-lxxix is used.

-   lxxxi. The method of embodiment lxxx, comprising the steps of:

-   a) contacting a liquid sample comprising an immunoglobulin with a    separation matrix according to any one of embodiments li-lxxix,

-   b) washing said separation matrix with a washing liquid,

-   c) eluting the immunoglobulin from the separation matrix with an    elution liquid, and

-   d) cleaning the separation matrix with a cleaning liquid.

-   lxxxii. The method of embodiment lxxxi, wherein the cleaning liquid    is alkaline, such as with a pH of 13-14.

-   lxxxiii. The method of embodiment lxxxi or lxxxii, wherein the    cleaning liquid comprises 0.1-1.0 M NaOH or KOH, such as 0.5-1.0 M    or 0.4-1.0 M NaOH or KOH.

-   lxxxiv. The method of any one of embodiments lxxxi-lxxxiii, wherein    steps a)-d) are repeated at least 10 times, such as at least 50    times or 50-200 times.

-   lxxxv. The method of any one of embodiments lxxxi-lxxxiv, wherein    steps a)-c) are repeated at least 10 times, such as at least 50    times or 50-200 times and wherein step d) is performed after a    plurality of instances of step c), such as at least 10 or at least    50 times.

1. A separation matrix comprising at least 15 mg/ml Fc-binding ligandscovalently coupled to a porous support, wherein: a) said ligandscomprise multimers of alkali-stabilized Protein A domains, b) saidporous support comprises cross-linked polymer particles having avolume-weighted median diameter (d50,v) of from 56 micrometers to 70micrometers and a dry solids weight of from 55 mg/ml to 80 mg/ml.
 2. Theseparation matrix of claim 1, wherein said cross-linked polymerparticles have a volume-weighted median diameter (d50,v) of from 56micrometers to 66 micrometers.
 3. The separation matrix of claim 1,wherein said cross-linked polymer particles have a dry solids weight offrom 60 mg/ml to 78 mg/ml.
 4. The separation matrix of claim 3, whereinsaid cross-linked polymer particles have a dry solids weight of from 65mg/ml to 78 mg/ml.
 5. The separation matrix of claim 1, wherein saidseparation matrix has a max pressure of at least 0.58 MPa when packed at300 +/−10 mm bed height in a 35 mm separation column
 6. The separationmatrix of claim 1, wherein said cross-linked polymer particles comprisecross-linked polysaccharide particles.
 7. The separation matrix of claim1, wherein said cross-linked polymer particles comprise cross-linkedagarose particles.
 8. The separation matrix of claim 1, wherein saidcross-linked polymer particles have a pore size corresponding to aninverse gel filtration chromatography Kd value of 0.69-0.85 for dextranof Mw 110 kDa.
 9. The separation matrix of claim 1, wherein saidmultimers comprise tetramers, pentamers, hexamers or heptamers ofalkali-stabilized Protein A domains.
 10. The separation matrix of claim1, wherein said multimers comprise hexamers of alkali-stabilized ProteinA domains.
 11. The separation matrix of claim 1, having a 10%breakthrough dynamic binding capacity for IgG of at least 45 mg/ml at2.4 mM residence time.
 12. The separation matrix of claim 1, having a10% breakthrough dynamic binding capacity for IgG of at least 60 mg/mlat 6 mM residence time.
 13. The separation matrix of claim 11, whereinthe 10% breakthrough dynamic binding capacity for IgG at 2.4 mMresidence time is reduced by less than 20% after incubation 31 h in 1.0M aqueous NaOH at 22 +/−2 C.
 14. The separation matrix of claim 1,having a dissociation constant for IgG2 of below 0.2 mg/ml in 20 mMphosphate buffer, 180 mM NaCl, pH 7.5.
 15. The separation matrix ofclaim 1, wherein said alkali-stabilized Protein A domains comprise anFc-binding polypeptide having an amino acid sequence as defined by, orhaving at least 80% identity to SEQ ID NO:53 and (SEQ ID NO: 53)X₁Q X₂AFYEILX₃LP NLTEEQRX₄X₅F IX₆X₇LKDX₈PSX₉SX₁₀X₁₁X₁₂LAEAKX₁₃ X₁₄NX₁₅AQ

wherein individually of each other: X₁=A or Q or is deletedX₂=E,K,Y,T,F,L,W,I,M,V,A,H or R X₃=H or K X₄=A or N X₅=A, G,S,Y,Q,T,N,F,L,W,I,M,V,D,E,H,R or K X₆=Q or E X₇=S or K X₈=E or D X₉=Q orV or is deleted X₁₀=K,R or A or is deleted X₁₁=A,E or N or is deletedX₁₂=I or L X₁₃=K or R X₁₄=L or Y X₁₅=D, F,Y,W,K or R.
 16. The separationmatrix of claim 15, wherein individually of each other: X₁=A or isdeleted, X₂=E, X₃=H, X₄=N, X₆=Q, X₇=S, X₈=D, X₉=V or is deleted, X₁₀=Kor is deleted, X₁₁=A or is deleted, X₁₂=I, X₁₃=K, X₁₄=L.
 17. Theseparation matrix of claim 15, wherein said multimers comprise hexamersof alkali-stabilized Protein A domains.
 18. The separation matrix ofclaim 15, wherein the amino acid sequence has at least 90% identity toSEQ ID NO:53.
 19. The separation matrix of claim 15, wherein the aminoacid sequence has at least 95% identity to SEQ ID NO:53.
 20. Theseparation matrix of claim 15, wherein the amino acid sequence has atleast 98% identity to SEQ ID NO:53.
 21. The separation matrix of claim15, wherein the amino acid sequence is identical to SEQ ID NO:53. 22.The separation matrix of claim 1, wherein the polypeptides are linked bylinkers comprising up to 25 amino acids.
 23. The separation matrix ofclaim 1, wherein at least two polypeptides are linked by linkerscomprising or consisting essentially of a sequence having at least 90%identity with an amino acid sequence selected from the group consistingof APKVDAKFDKE (SEQ ID NO:96, APKVDNKFNKE (SEQ ID NO:97), APKADNKFNKE(SEQ ID NO:98), APKVFDKE (SEQ ID NO:99), APAKFDKE (SEQ ID NO:100),AKFDKE (SEQ ID NO:101), APKVDA (SEQ ID NO:102), VDAKFDKE (SEQ IDNO:103), APKKFDKE (SEQ ID NO:104), APK, APKYEDGVDAKFDKE (SEQ ID NO:105)and YEDG (SEQ ID NO:106).
 24. The separation matrix of claim 1,comprising from 15 mg/ml to 21 mg/ml Fc-binding ligands covalentlycoupled to the porous support.
 25. The separation matrix of claim 1,comprising from 17 mg/ml to 21 mg/ml Fc-binding ligands covalentlycoupled to the porous support.
 26. The separation matrix of claim 1,comprising from 18 mg/ml to 20 mg/ml Fc-binding ligands covalentlycoupled to the porous support.
 27. The separation matrix of claim 1having a 10% breakthrough dynamic binding capacity for IgG of at least50 mg/ml at 2.4 min residence time.
 28. The separation matrix of claim 1having a 10% breakthrough dynamic binding capacity for IgG of at least55 mg/ml at 2.4 min residence time.
 29. The separation matrix of claim1, having a 10% breakthrough dynamic binding capacity for IgG of atleast 65 mg/ml at 6 min residence time.
 30. The separation matrix ofclaim 1, having a 10% breakthrough dynamic binding capacity for IgG ofat least 70 mg/ml at 6 min residence time.
 31. The separation matrix ofclaim 1, having a 10% breakthrough dynamic binding capacity for IgG ofat least 75 mg/ml at 6 min residence time.
 32. The separation matrix ofclaim 1 having a dissociation constant for IgG2 of below 0.1 mg/ml in 20mM phosphate buffer, 180 mM NaCl, pH 7.5.
 33. A method of isolating animmunoglobulin, comprising the steps of: a) contacting a liquid samplecomprising an immunoglobulin with a separation matrix according to claim1, b) washing said separation matrix with a washing liquid, c) elutingthe immunoglobulin from the separation matrix with an elution liquid,and d) cleaning the separation matrix with a cleaning liquid.
 34. Themethod of claim 33, wherein the cleaning liquid comprises from 0.1 to1.0 M NaOH or KOH.
 35. The method of claim 33, wherein steps a)-d) arerepeated at least 10 times.
 36. The method of claim 33, wherein in stepd) said elution liquid has a pH of from 2.5 to 4.5.
 37. The method ofclaim 33, wherein in step b) the pH is from 6 to
 8. 38. The method ofclaim 33, wherein in step b) the residence time of said liquid sample onsaid separation matrix is from 2 minutes to 20 minutes.
 39. The methodof claim 33, wherein the cleaning liquid comprises at least 0.5 M NaOH.40. The method of claim 33, wherein in step e) the contact time betweenthe separation matrix and the cleaning liquid is less than 10 min.